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Home My WebLink AboutNC0000396_SARP_Rev 0_Narrative_20161219SITE ANALYSIS AND REMOVAL PLAN ASHEVILLE STEAM ELECTRIC GENERATING PLANT REVISION 0 Prepared Tor DUKE ENERGY. Dukc Eneryy 55U South I ryon Street Charlotte, North Carolina 28202 Dcuumber 2016 Prepared by ame: 4 foster whrelcr Amec Foster Wneeler Environment & Infrastructure, Inc. Project No. 7810160620 111177 Z y a SEAL 043443 = _ R . 1 � �2 l(fT1r, Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 i EXECUTIVE SUMMARY Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) has prepared this Site Analysis and Removal Plan (Removal Plan) in support of the proposed closure of the Coal Combustion Residuals (CCR) Basins (Ash Basins) at the Asheville Steam Electric Generating Plant (Asheville Plant) located near Arden, North Carolina. The purpose of this Removal Plan is to seek the North Carolina Department of Environmental Quality’s (NCDEQ) concurrence with the Duke Energy Progress, LLC (Duke) plan for closure of the Ash Basins located at the Asheville Plant. This Removal Plan is submitted to NCDEQ on behalf of Duke. The work to be performed in support of the closure of the Ash Basins is summarized in this document, which is consistent with the requirements of the Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals from Electric Utilities Rule (CCR Rule) [EPA, 2015] and the NC Coal Ash Management Act (CAMA). This Removal Plan is based on engineering and environmental factors minimizing the impacts to communities and managing cost. The drawings presented herein are accurate at the time of preparing this Removal Plan and are subject to change pending further discussion with Duke. The closure option entails excavation of CCR within the Ash Basins and transport for beneficial use or placement in an off- site permitted landfill. The two Ash Basins located at the Asheville Plant include: (i) the 1982 Ash Basin; and (ii) the 1964 Ash Basin. Excavation of the 1982 Ash Basin was completed on September 30, 2016, and the basin was turned over for dam decommissioning and the construction of a natural gas combined cycle plant after an independent qualified professional engineer concluded that primary source ash had been removed from the basin. Duke estimates the tonnage of ash in the 1964 Ash Basin to be approximately 2.9 million tons as of December 31, 2016. Subsequent to removal of the ash pursuant to the Coal Combustion Residual Removal Verification Procedure, Duke will implement its Excavation Soil Sampling Plan, as referenced in the Construction Quality Assurance Plan, in a manner that meets the closure performance standards set out in Part II, Section 3.(c) of CAMA and Section 257.102(c) of the CCR Rule. Assessment activities for the Asheville Plant were performed by SynTerra, Corp. (SynTerra) and were reported in a Comprehensive Site Assessment (CSA) report dated August 23, 2015, a CSA Supplement 1 dated August 31, 2016, a Corrective Action Plan (CAP) Part 1 dated November 20, 2015, and a CAP Part 2 dated February 19, 2016. Groundwater receptor surveys were conducted for the site. In addition to identification of receptors, the compiled data was used to develop a description of the site, surrounding area, geology, and hydrogeology, including a Site Hydrogeologic Conceptual Model (SCM). The Constituents of Interest (COI) identified from the Asheville Plant ash material and pore water sample analyses include antimony, arsenic, boron, chromium, cobalt, iron, manganese, sulfate, thallium, TDS, vanadium, and pH. These COIs are identified as exceeding either the 2L or Interim Maximum Allowable Concentrations (IMAC) in at least one ash pore water monitoring well. Groundwater trend analysis modeling showed that COIs with exceedances of the 2L or IMAC are identified in all compliance boundary wells at statistically elevated values over concentrations observed in designated background wells. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 ii A preliminary geotechnical evaluation was performed and is presented in this Removal Plan. The results of the investigations indicate that the subsurface materials primarily consist of, from top to bottom, CCR (within the 1964 Ash Basin) or Dike Fill (at the perimeters of the basins) and residual soils (sitting on bedrock). A partially weathered rock zone was encountered at the transition between the residual soils and the bedrock (gray to dark gray, fine to medium-grained gneiss). The closure of the Ash Basins will entail the following activities: CCR will be excavated and transported from the site for beneficial use or placement in an off-site permitted landfill. Per the current plan, after establishing the final design grades, the footprints of the 1982 Ash Basin will become the site for a planned combined cycle plant, and the 1964 Ash Basin footprint will be graded to drain. The potential future use of the 1964 Ash Basin is undetermined at this time. This Removal Plan also presents a summary of the engineering evaluation and analyses performed, as well as a Construction Quality Assurance (CQA) Plan. The Wastewater and Stormwater Plans, including a plan for obtaining the required permits, are described in a preliminary manner in this Removal Plan. These plans will be developed and submitted under a separate cover. Anticipated permits required for closure of the Ash Basins are identified and listed in this Removal Plan. A Post-Closure Care Plan is provided, including the groundwater monitoring program currently under evaluation by NCDEQ. This Removal Plan presents the estimated milestones related to basin closure and post-closure activities. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 iii LIST OF ACRONYMS AND ABBREVIATIONS Acronym/ Abbreviation Definition µg/L Microgram per liter 2B NCAC Title 15A, Subchapter 2B. Surface Water and Wetland Standards 2L NCAC Title 15A, Subchapter 2L. Groundwater Classification and Standards ASTM American Society for Testing Materials CAMA Coal Ash Management Act CAP Corrective Action Plan CCP Coal Combustion Products CCR Coal Combustion Residual CCR Rule Coal Combustion Residuals Rule CFR Code of Federal Regulations CMS Closure Model Scenario cm/sec centimeters per second CMP Corrugated Metal Pipe COI Constituent of Interest CQA Construction Quality Assurance CSA Comprehensive Site Assessment CY Cubic Yards DWQ Division of Water Quality DWR Division of Water Resources (formerly DWQ) EDXRF EMP Energy Dispersive X-Ray Fluorescence Effectiveness Monitoring Plan EPSC Erosion Prevention and Sediment Control FGD Flue Gas Desulfurization gal/min gallons per minute GAP Groundwater Assessment Work Plan GIS Geographic Information System HDPE High Density Polyethylene IMAC IMP Interim Maximum Allowable Concentrations Interim Monitoring Plan MDE Maximum Design Earthquake mL/g milliliters per gram MPD Master Programmatic Document MSD Metropolitan Sewerage District MW Megawatt NAVD 88 North American Vertical Datum of 1988 NCDENR North Carolina Department of Environment and Natural Resources NCDEQ North Carolina Department of Environmental Quality (formerly NCDENR) NOI Notice of Inspection NPDES National Pollutant Discharge Elimination System O&M Operations and Maintenance OM&M Operations Maintenance and Monitoring pcf Pounds per Cubic Foot Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 iv Acronym/ Abbreviation Definition Plant Asheville Steam Electric Generating Plant PMP Probable Maximum Precipitation psf Pounds per Square Foot PWR Partially Weathered Rock RCP Reinforced Concrete Pipe RSL USEPA Regional Screening Level S.B. Senate Bill SCM Site Conceptual Model SPLP Synthetic Precipitation Leaching SPT Standard Penetration Test TBD To be determined TDS Total Dissolved Solids TOC Total Organic Carbon Tsf Tons per square foot UNCC University of North Carolina, Charlotte USACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency USGS U.S. Geological Survey XRD X-Ray Diffraction Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 v TABLE OF CONTENTS RECORD OF REVISION ........................................................................................................... ix 1.INTRODUCTION ............................................................................................................. 1 1.1 Site Analysis and Removal Plan Objectives ....................................................................... 1 1.2 Document Organization ...................................................................................................... 1 2.GOVERNING REGULATIONS ........................................................................................ 2 2.1 Federal CCR Rules ............................................................................................................. 2 2.2 North Carolina ..................................................................................................................... 2 3.FACILITY DESCRIPTION AND EXISTING SITE FEATURES ........................................ 5 3.1 Surface Impoundment Description ...................................................................................... 5 3.1.1 Site History and Operations ................................................................................... 5 3.1.2 Estimated Volume of CCR Materials in Impoundments ........................................ 7 3.1.3 Description of Surface Impoundment Structural Integrity ...................................... 8 3.1.4 Sources of Discharges into Surface Impoundments.............................................. 9 3.1.5 Existing Liner System ............................................................................................ 9 3.1.6 Inspection and Monitoring Summary ..................................................................... 9 3.2 Site Maps .......................................................................................................................... 13 3.2.1 Summary of Existing CCR Impoundment Related Structures ............................. 13 3.2.2 Receptor Survey .................................................................................................. 14 3.2.3 Existing On-Site Landfills ..................................................................................... 17 3.3 Monitoring and Sampling Location Plan ........................................................................... 17 3.3.1 Interim Groundwater Monitoring Plan .................................................................. 17 4.RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL INVESTIGATIONS ........................................................................................................ 19 4.1 Hydrogeology and Geologic Descriptions ......................................................................... 19 4.1.1 Regional Geology ................................................................................................ 19 4.1.2 Regional Hydrogeology ........................................................................................ 19 4.2 Stratigraphy of the Geologic Units Underlying Surface Impoundments ........................... 20 4.3 Hydraulic Conductivity Information ................................................................................... 20 4.4 Geotechnical Properties .................................................................................................... 21 4.5 Chemical Analysis of Impoundment Water, CCR Materials and CCR Affected Soil ........ 31 4.5.1 Source Area(s) Characterization.......................................................................... 31 4.5.2 Surface Water and Sediment Assessment .......................................................... 33 4.6 Historical Groundwater Sampling Results ........................................................................ 34 4.6.1 Summary of Surficial Aquifer Results .................................................................. 35 4.6.2 Summary of Transitional Zone Aquifer Results ................................................... 36 4.6.3 Summary of Bedrock Aquifer Results .................................................................. 37 Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 vi 4.7 Groundwater Potentiometric Contour Maps ..................................................................... 37 4.8 Figures: Cross Sections Vertical and Horizontal Extent of CCR within the Impoundments .......................................................................................................................................... 39 5.GROUNDWATER MODELING ANALYSIS................................................................... 41 5.1 Site Conceptual Model ...................................................................................................... 42 5.2 Geochemical Modeling ..................................................................................................... 44 5.2.1 Soil Sorption Evaluation ....................................................................................... 44 5.2.2 Geochemical Numerical Modeling Analysis ......................................................... 46 5.3 Numerical Groundwater and Transport Modeling ............................................................. 47 5.3.1 Numerical Groundwater Flow Model Description ................................................ 48 5.3.2 Numerical Groundwater Transport Model Description ......................................... 49 5.4 Groundwater Chemistry Effects ........................................................................................ 49 5.5 Groundwater Trend Analysis Methods .............................................................................. 52 6.BENEFICIAL REUSE AND FUTURE USE ................................................................... 53 6.1 CCR Material Reuse ......................................................................................................... 53 6.2 Site Future Use ................................................................................................................. 53 7.CLOSURE DESIGN DOCUMENTS .............................................................................. 54 7.1 Engineering Evaluations and Analyses ............................................................................ 54 7.2 Site Analysis and Removal Plan Drawings ....................................................................... 54 7.3 Construction Quality Assurance Plan ............................................................................... 54 8.MANAGEMENT OF WASTEWATER AND STORMWATER ........................................ 55 8.1 Stormwater Management .................................................................................................. 55 8.2 Wastewater Management ................................................................................................. 55 9.DESCRIPTION OF FINAL DISPOSITION OF CCR MATERIALS ................................. 56 10.APPLICABLE PERMITS FOR CLOSURE .................................................................... 57 11.POST CLOSURE MONITORING AND CARE ............................................................... 58 11.1 Groundwater Monitoring Program ..................................................................................... 58 12.PROJECT MILESTONES AND COST ESTIMATES ..................................................... 60 12.1 Project Schedule ............................................................................................................... 60 12.2 Closure and Post-Closure Cost Estimate ......................................................................... 60 13.REFERENCED DOCUMENTS ...................................................................................... 61 Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 vii Tables Table 2-1 Federal CCR Rule Closure Plan Requirements, Summary and Cross Reference Table Table 2-2 NC CAMA Closure Plan Requirements, Summary and Cross Reference Table Table 3-1 1982 Ash Basin Dam Summary Recommendations (Amec Foster Wheeler 2016b) Table 3-2 1964 Ash Basin Dam Summary Recommendations (Amec Foster Wheeler 2016b) Table 4-1 Summary of Hydraulic Conductivity Geometric Mean Monitoring W ell Slug Testing Results for Each Hydrogeologic Zone Table 4-2 Unit Weight and Shear Strength Parameters for the 1982 Ash Basin Dam Table 4-3 Unit Weight and Shear Strength Parameters for the 1964 Ash Basin Dam Table 4-4 Unit Weight and Shear Strength Parameters for the Separator Dike Table 4-5 Index Property Test Results of Materials in 1982 Ash Basin Table 4-6 Index Property Test Results of Materials in 1964 Ash Basin Figures Figure 1 Site Location Map Figure 2 Site Overview Aerial Plan Figure 3 CCR Impoundment Related Structures Figure 4 Boring Location Map 1982 and 1964 Ash Basins Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 viii Appendices Appendix A Waste Inventory Analysis (1964 Ash Basin) Appendix B SynTerra Comprehensive Site Assessment Report Tables and Figures Appendix C SynTerra Corrective Action Plan Tables and Figures Appendix D Engineering Evaluations and Analyses of Closure Design Grading Plans for the 1982 Ash Basin Appendix E Dam Decommissioning and Ash Removal Closure Plan Drawings for the 1982 Ash Basin Appendix F Construction Quality Assurance Plan Appendix G Post-Closure Operations Maintenance and Monitoring (OM&M) Plan Appendix H Closure and Post-Closure Care Cost Estimates (to be added at a later date) Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 ix RECORD OF REVISION Revision Number Revision Date Section Revised Reason for Revision Description of Revision 0 12/2016 N/A N/A Initial Issue 1 2 Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 1 1. INTRODUCTION Duke intends to close the 1982 and 1964 Ash Basins at the Asheville Steam Electric Generating Plant (Plant). Both basins will be closed by removal of the coal ash for transport for beneficial use or an off-site fully lined landfill. The purpose of this document is to outline and present the plan and objectives to achieve closure for the ash basins and meet the requirements of the North Carolina Coal Ash Management Act (CAMA) and the Coal Combustion Residuals (CCR) Rule (CCR Rule). 1.1 Site Analysis and Removal Plan Objectives The objective of this Site Analysis and Removal Plan (Removal Plan) is to set out the process for closing the 1982 and 1964 Ash Basins at the Plant in accordance with applicable regulations, including the Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals from Electric Utilities Rule (CCR Rule) (EPA, 2015) and the North Carolina Coal Ash Management Act (CAMA) for closure of CCR surface impoundments. 1.2 Document Organization Although closure of the CCR surface impoundments at the Asheville facility is solely controlled by Part II, Sections 3.(b) and 3.(c) of CAMA (and not N.C.G.S. § 130A-309.214), for purposes of consistency with the closure plans for those non-high-priority Duke facilities to which N.C.G.S. § 130A-309.214 applies, this Removal Plan is structured to follow generally the closure plan elements set forth in N.C.G.S § 130A-309.214(a)(4). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 2 2. GOVERNING REGULATIONS 2.1 Federal CCR Rules The CCR Rule was published in the Federal Register on April 17, 2015. This rule regulates CCR as a nonhazardous waste under Subtitle D of the Resource Conservation and Recovery Act. The effective date of the rule is October 19, 2015. Written closure plan requirements are set forth in 40 CFR § 257.102(b)(1) of the CCR Rule and are summarized in Table 2-1 of this document. Table 2-1 provides a cross reference between each regulatory closure plan requirement and the corresponding Removal Plan section(s) where that requirement is addressed. The CCR Rule requires that a history of construction be developed for each CCR unit as described in 40 CFR § 257.73(c)(1), and 40 CFR §257.105(f)(9) requires that this history of construction be maintained in the facility’s written operating record. In addition, §§ 257.106(f)(8) and 257.107(f)(8) require notification of the availability of the history of construction to the State Director and posting of this information on the publicly accessible CCR Website, respectively. The History of Construction Report (Amec Foster Wheeler 2016a) has been developed as a primary source of information reported in the Removal Plan and to satisfy these record keeping requirements. 2.2 North Carolina In August 2014, the North Carolina General Assembly passed Senate Bill (S.B.) 729 (known as CAMA), which lists specific regulatory requirements for CCR surface impoundment closure. For the Plant, “surface impoundment,” as defined in N.C.G.S. § 130A-309.201(6), is interpreted to include the 1982 Ash Basin and 1964 Ash Basin. Part II, Section 3(b) of CAMA deems the Plant a “high-priority” site and specifically requires closure by August 1, 2019, which entails dewatering the ash basins to the maximum extent practicable and removing and transferring CCR from basins to a lined landfill or structural fill. However, the North Carolina Mountain Energy Act of 2015 extended the closure date to August 1, 2022. Note that ash removal is required to be complete by August 1, 2022; however, dam decommissioning and final grading of the former ash basin areas and completion of corrective actions to restore groundwater quality, if needed, as provided in N.C.G.S. § 130A-309.204, may extend beyond this date. CAMA’s closure plan requirements applicable to non-high-priority sites were codified at N.C.G.S. § 130A-309.214(a)(4), which requires plans for such sites to include the elements listed below. Although, as noted in Section 1.2 above, N.C.G.S. § 130A-309.214 is not specifically applicable to the Plant, which is a high-priority site required to close pursuant to Part II, Sections 3.(b) and 3.(c) of CAMA, this Removal Plan relies on N.C.G.S. § 130A-309.214(a)(4) solely to inform its organization. A closure plan will be required for each CCR surface impoundment subject to N.C.G.S. § 130A- 309.214(a)(4) regardless of its risk classification. CAMA defines the requirements for these Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 3 closure plans in N.C.G.S. §130A-309.214(a)(4). The CAMA closure plan regulations are summarized in Table 2-2 for reference. The Closure Plan shall include the following:  Facility description;  Site maps;  Hydrogeologic, geologic, geotechnical characterization results;  Groundwater potentiometric maps and extent of contaminants of concern;  Groundwater modeling;  Description of beneficial reuse plans;  Removal Plan drawings, design documents, and specifications;  Description of the construction quality assurance and quality control program;  Description of wastewater disposal and stormwater management provisions;  Description of how the final disposition of CCR will be provided;  List of applicable permits to complete closure;  Description of post-closure monitoring and care plans;  Estimated closure and post-closure milestone dates;  Estimated costs of assessment, corrective action, closure and post-closure care; and  Future site use description. In addition to the closure pathway and closure plan requirements, CAMA outlines groundwater assessment and corrective action requirements summarized as follows:  Submit Groundwater Assessment Plans by December 31, 2014;  Within 180 days of Groundwater Assessment Plan approval, complete a groundwater assessment and submit a Groundwater Assessment Report; and  Provide a Corrective Action Plan (if required) within 90 days (and no later than 180 days) of Groundwater Assessment Report completion. The groundwater assessment and corrective action activities for the Plant are currently being developed by SynTerra Corp. (SynTerra). The Comprehensive Site Assessment (CSA) Report for the Plant was completed on August 23, 2015 (SynTerra 2015a). Duke has been in correspondence with the NCDEQ and has received permission to submit a Corrective Action Plan (CAP) in two parts. The first part of the CAP was submitted on November 20, 2015, and includes background information; a brief summary of the CSA findings; a brief description of site geology and hydrogeology; a summary of the previously completed receptor survey; a description of NCAC Title 15A Subchapter 2L. Groundwater Standards (2L Standards) and NCAC Title 15A NCAC Subchapter 2B. Surface Water Standards (2B Standards) exceedances; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 4 proposed site-specific groundwater background concentrations; a description of the site conceptual model; and groundwater flow, and transport modeling (SynTerra 2015b). The second part of the CAP was submitted on February 19, 2016, and includes risk assessment, alternative methods for achieving restoration, conceptual plans for recommended corrective actions, implementation schedule, and a plan for future monitoring and reporting (SynTerra 2016a). The CSA Supplement 1 was also issued on August 31, 2016, and addresses the following (SynTerra 2016b):  Summary of groundwater monitoring data through July 2016;  Reponses to NCDEQ review comments pertaining to the CSA;  Update on the development of provisional background groundwater concentrations (through April 2016 data);  Findings from assessment activities conducted since the submittal of the CSA report, including data gaps previously identified in the CSA; and  Description of planned additional assessment activities. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 5 3. FACILITY DESCRIPTION AND EXISTING SITE FEATURES 3.1 Surface Impoundment Description 3.1.1 Site History and Operations The Plant is a coal-combustion generating facility that began commercial operation in 1964. Ash basins, which support operations at the Plant, were expanded or otherwise modified in 1971, 1999, and 2000. As shown on Figure 1, the facility is located in Buncombe County in Western North Carolina, approximately 8 miles south of the City of Asheville, and is within the U.S. Geological Survey (USGS) Skyland Quadrangle. The center of the facility is at the approximate coordinates: latitude 35°28’N, longitude 82°32’W. The Plant is situated on approximately 786 acres, including areas on both sides of Interstate 26 (I-26). The Plant consists of two coal-fired generating units with a combined power generating capacity of 376 megawatts (MW), two combustion turbine units with a combined 324 MW capacity, two CCR units known as the 1982 Ash Basin and the 1964 Ash Basin, and obtains makeup water from Lake Julian. Figure 2 includes an aerial photo of the Plant that also shows the associated and surrounding features. The two ash basin dams fall under the jurisdiction of the NCDEQ Division of Energy, Mineral and Land Resources, Land Quality Section, Dams Program and are listed under State ID Number BUNCO-089 (1982 Ash Basin) and BUNCO-097 (1964 Ash Basin). According to the current NCDEQ hazard-rating criteria, the dams are considered to be large, high-hazard structures, falling under Class C dam classification based on potential breach impacts to potential loss of life and/or economic damage. Fly ash and bottom ash have been deposited within the facility’s two ash basins by hydraulic sluicing. Ash is currently sluiced to the Rim Ditch system, where it is dewatered and temporarily stored within the 1964 Ash Basin. Ash is later removed and transported off-site for beneficial reuse or proper disposal. Decant water from the Rim Ditch is pumped through a center pond filter system to the stilling basin located to the north of the 1964 Ash Basin, and then out through NPDES Outfall 001. Some stormwater and wastewater from portions of the Plant site is routed into the Duck Pond and then pumped into to the head of the Rim Ditch for treatment. Following is a brief summary from the History of Construction report (Amec Foster Wheeler 2016a) of each of the Ash Basins. 1964 Ash Basin and Equalization Basin The 1964 Ash Basin Dam was part of the original steam plant construction designed by Ebasco in 1962. The dam was constructed as a compacted, random earth fill embankment with a design crest elevation of approximately 2125 feet. The 1964 Ash Basin has a drainage area of approximately 75 acres according to the NCDEQ dam database. In 1970–71, the dam was extended and raised approximately 30 feet to a planned crest elevation of 2157.5 feet to provide additional ash storage. This raising necessitated a separator Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 6 dike east of the main dam. Recent survey information shows a spot crest low point elevation of approximately 2157.3 feet (North American Vertical Datum of 1988 [NAVD 88]). Sluicing of ash to the 1964 Ash Basin ceased in 1982 with the construction of the 1982 Ash Basin. In 2005, an engineered wetlands treatment system for flue gas desulfurization (FGD) process wastewater was constructed within the northwestern portion of the 1964 Ash Basin. The system consisted of two equalization basins that routed wastewater from the FGD process to a series of lined ponds that contained vegetation to treat the wastewater. The constructed wetlands and equalization basins were designed by Parsons E&C (now known as Worley Parsons). In 2012, a 1964 Dam improvement project was initiated to improve the stability of the dam. This improvement project included:  Extension of the core of the dam along the crest;  Installation of a toe drain along the base of the downstream slope of the dam that routes collected water into an existing concrete structure;  Abandonment of the 30-inch-diameter concrete spillway pipe and riser by grouting in- place;  Construction of a riprap buttress along the toe of the dam; and  Modification of the path for discharge from the wetlands system and 1982 Ash Basin. In parallel with the dam improvements, a drainage improvement project designed by MACTEC (now Amec Foster Wheeler) was completed to redirect the outflow from the 1982 Ash Basin riser structure into buried piping (high density polyethylene [HDPE] encased in flowable fill) installed within the 1964 Ash Basin area to the interior of the Duck Pond, and from the Duck Pond to a new outlet structure at the French Broad River. With this project, the spillway for the 1964 Ash Basin is located within the Duck Pond in the northeast corner of the basin and connected to the drainage pipe system installed in 2012. For more detailed information and area capacity curves for the basin, refer to the History of Construction report (Amec Foster Wheeler 2016a). The equalization basins and engineered wetlands were removed to provide an area to temporarily place ash excavated from the 1982 Ash Basin. During 2016, wastewater flows and treatment were adjusted to facilitate the excavation of the 1982 Basin. The center pond filters were constructed at the end of the Rim Ditch and commissioned to replace the treatment provided by the Duck Pond. Infrastructure was developed to dewater the Duck Pond to the head of the Rim Ditch, and subsequently, the low volume waste and stormwater that flowed into the 1982 Basin and pumped to the Rim Ditch was re-routed to the Duck Pond. All treated effluent is discharged to Outfall 001. 1982 Ash Basin and Separator Dike The 1982 Ash Basin Dam was designed by CP&L Engineers and W.L. Wells in 1981. The ash basin dam was constructed of compacted random earth fill in 1981–82 and ash storage began in 1982 (when the 1964 Ash Basin was removed from service). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 7 The dam is approximately 1500 feet long with a design crest elevation at 2165 feet. Recent survey information before dam decommissioning activities began showed spot elevations ranging from 2164.5 feet to 2165.7 feet (NAVD 88). The west end of the dam joins the abutment of the 1964 Ash Basin Dam and the east end ties into a natural knoll. An internal drainage blanket connected to toe-drainage piping provides seepage control. The 1982 Ash Basin has a drainage area of approximately 70 acres, according to the NCDEQ dam database. When the 1964 Ash Basin dam was raised in 1970–71, a Separator Dike was constructed across a topographic low area on the east side of the 1964 Ash Basin. The 1982 Ash Basin design included raising the Separator Dike due to the planned higher crest elevation of the 1982 Ash Basin Dam. The Separator Dike was built on a native soil base; fill for the dike was not placed on ash. The outfall skimmer was near the southwest corner of the 1982 Ash Basin. It connected to a drainage pipe that was installed in 2012 that runs below the constructed wetlands (now removed) and the northern portion of the 1964 Ash Basin, before connecting to a stilling basin and concrete outfall structure at the French Broad River. For more detailed information and area capacity curves for the basin, refer to the History of Construction report (Amec Foster Wheeler 2016a). The 1982 Ash Basin began to reach capacity in 2007. To facilitate continued Plant operations, an ash excavation plan was developed to increase ash storage capacity. As part of this plan, ash was transported to the Asheville Regional Airport (Airport) and beneficially used as structural fill. The structural fill project areas 1, 4, and 3 were completed in 2015. In October 2015, operations began to transport ash to an off-site fully lined landfill near Homer, Georgia. As ash removal operations were conducted within the 1982 Ash Basin, the outfall skimmer was disconnected from the drainage pipe, because sufficient volume existed in the 1982 Ash Basin to store the PMP storm event. Ash removal within the 1982 Ash Basin was completed on September 30, 2016, and decommissioning of the dam is currently underway. 3.1.2 Estimated Volume of CCR Materials in Impoundments The volume of CCR material contained in the ash basins is presented below. Throughout this document, ash volumes are expressed as tons using the conversion of 1.2 tons per cubic yard (tons/yd3). Excavation of the 1982 Ash Basin was completed on September 30, 2016, and the Basin was turned over for dam decommissioning and the construction of a natural gas combined cycle plant. The volume of ash currently in the 1964 Ash Basin is estimated to be approximately 2,900,000 tons as of December 31, 2016 (Duke Energy 2016). A Waste Inventory Analysis, dated January 2015 (Amec Foster Wheeler 2015c), was performed for the 1964 Ash Basin. Since that date some ash from the 1982 Ash Basin was temporarily placed in the 1964 Ash Basin ash stack in 2016. The plant also continues to generate ash resulting from the operation of the coal-fired units, until they are retired from operation. The Waste Inventory Analysis is an estimation of the Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 8 volume of ash present at the time, but does not include the subsequent ash placed within the basin due to ash stacking operations or generation ash production. The Waste Inventory Analysis calculations were performed using historical ground surface topographic information from historical design drawings or USGS mapping, and used AutoCAD Civil 3D software to compare the historical ground surface elevation contours with current conditions. In these calculations, an approximate pre-fill ground surface was generated, and pre-fill grades were compared to current North Carolina Flood Plain Mapping LIDAR topography. The Waste Inventory Analysis for the 1964 Ash Basin (including report and calculations) is included with this document as Appendix A. All of the ash will be removed from the 1964 Ash Basin prior to dam decommissioning and ash basin closure. 3.1.3 Description of Surface Impoundment Structural Integrity A Reconstitution of Ash Basin Design (Amec Foster Wheeler 2015e) was performed for the 1982 and 1964 Ash Basins that compiled and analyzed pertinent information regarding the integrity of the embankments. As summarized below, this report examined the geotechnical properties, structural elements (spillways), and hydrology and hydraulics of the basins. The report compiled and analyzed existing reports and evaluations for the ash basins, and addressed data gaps with additional analyses and conclusions for the site. Additional information is presented in the History of Construction Report (Amec Foster Wheeler 2016a) in reference to the hydrologic and hydraulic studies performed after the issuance of the Reconstitution of Ash Basin Design report. In addition, an additional geotechnical stability analysis was performed by AECOM (AECOM 2016) for the 1964 Ash Basin dam. This analysis analyzed the potential for liquefaction and seismic stability of the embankment to determine if stability improvements to the dam were needed. Based on a review of the historical documents and additional data gathered, the following conclusions were reached for the ash basins and related structures: Geotechnical analyses show:  The minimum factors of safety for the 1964 Ash Basin Dam, 1982 Ash Basin Dam, the Separator Dike and the Equalization Basin dike were greater than the target factor of safety requirements for applicable loading conditions at all locations analyzed.  Seismic Site Class C and D were determined to be appropriate for the 1982 Dam/Separator Dike and Equalization Basin/1964 Dam area, respectively, prior to analysis of liquefaction.  Based on the Standard Penetration Test (SPT) analyses, widespread liquefaction of the foundation soils of the embankments is not anticipated for the design seismic event. The dams and dikes are not susceptible to liquefaction, and post-earthquake shearing failures of the impoundments are not anticipated. Displacements of the dam/dike crests are not expected. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 9 Structural analyses show:  The riser structure at the former Duck Pond within the 1964 Ash Basin could not be evaluated due to lack of information regarding the timber pile foundation system. By inspection, it was concluded that this structure was not designed for seismic events and it would likely fail under seismic loading conditions.  The 1982 Ash Basin riser and outfall pipe were determined to be in poor condition. However, those structures have been abandoned as of the date of this Removal Plan. Hydrologic and Hydraulic:  All ash has been removed from the 1982 Ash Basin, and dam decommissioning activities are currently underway. The drawings for the dam decommissioning (Appendix E) address the sequencing of grading for removal of the embankment and backfilling to prohibit impounding water, and management of stormwater during this process.  The total storm volume in the 1964 Ash Basin for the full PMP event is approximately 183.7 acre feet, and the available storage volume is approximately 192.9 acre feet (Amec Foster Wheeler 2016a). 3.1.4 Sources of Discharges into Surface Impoundments The 1964 Ash Basin currently receives low volume stormwater, sluice water, and stormwater from the switchyards and gypsum pad. Both ash basins receive stormwater from their associated drainage areas. The sluicing operations and effluent discharges from the Plant have historically been routed to the ash basins. However, only the 1964 Ash Basin currently supports ongoing operations with the Duck Pond and the Rim Ditch. Ash is directed to the Rim Ditch, where generation ash is sluiced, recovered, and temporarily placed in the 1964 Ash Basin. The discharge of effluent from the Plant’s operation is permitted under NPDES Permit NC0000396 authorized by the NCDEQ Division of Water Resources (DWR). 3.1.5 Existing Liner System Based on historical documents, the 1982 and 1964 Ash Basins are not lined. 3.1.6 Inspection and Monitoring Summary Weekly, monthly, and annual inspections of the ash management facilities are conducted at the Plant consistent with the North Carolina CAMA and CCR Rule and in accordance with the Operations & Maintenance (O&M) Manual (Amec Foster Wheeler 2015d). The findings presented in this section are tracked and resolved in the pertinent work management system. Independent third-party inspections are performed once every year to promote the design, operation, and maintenance of the surface impoundment in accordance with generally accepted engineering standards. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 10 Annual inspections are performed to gather information on the current condition of the dams and appurtenant works. This information is then used to establish needed repairs and repair schedules, to assess the safety and operational adequacy of the dam, and to assess compliance activities with respect to applicable permits, environmental and dam regulations. Annual inspections are also performed to evaluate previous repairs. In May 2016, an annual inspection of the Plant ash basin dams was performed (Amec Foster Wheeler 2016b). This inspection included observations of the ash basin dams, discharge towers, and drainage pipes. In addition to the field observations of the physical features of the impoundments, this annual inspection included a review of available design documents and inspection records. This report included findings from previous inspections including, but not limited to, the following documents:  AMEC Environment & Infrastructure, Inc., “2014 Annual Ash Basin Dam Inspection, Asheville Steam Electric Station,” January 14, 2015;  Amec Foster Wheeler, “2015 Annual Ash Basin Dam Inspection, Asheville Plant,” May 9, 2016;  AMEC Environment & Infrastructure, Inc., “2012 Five-Year Independent Consultant Inspection, Cooling Lake Dam and Ash Pond Dams, Asheville Steam Electric Plant,” February 19, 2013;  S&ME Inc., “Construction Repair Certification Report, 1964 Ash Basin Dam Improvements (Phase II), Progress Energy Asheville Plant,” December 18, 2012;  NCDENR Notice of Inspection Reports for 1964 Ash Pond Dam (BUNCO-097) dated April 30, 2010; May 6, 2011; February 22, 2012; April 19, 2013; and April 1, 2014;  AMEC Environment & Infrastructure, Inc., “2013 Report of Limited Field Inspection, Cooling Lake Dam and Ash Pond Dams, Duke Energy Progress – Asheville Steam Electric Plant,” August 5, 2013;  AMEC Environment & Infrastructure, Inc., “2014 Report of Limited Field Inspection, Cooling Lake Dam and Ash Pond Dams, Duke Energy Progress – Asheville Steam Electric Plant,” August 28, 2014;  AMEC Environment & Infrastructure, Inc., “Asheville Plant, BUNCO-089-H, BUNCO-097- H Observations, 8/27/2014 through 10/2/2014, Buncombe County, North Carolina,” September 8, 2014, through October 6, 2014;  NCDENR Notice of Inspection Reports for 1982 Ash Pond Dam (BUNCO-089) dated May 5, 2010; May 6, 2011; February 22, 2012; April 19, 2013; and April 1, 2014;  Dewberry & Davis, Inc., “Final Coal Combustion Waste Impoundment Dam Assessment Report, Site 7, 1982 Pond & 1964 Pond, Progress Energy Carolinas, Asheville, North Carolina,” Revised Final September 11, 2009;  Stantec, “Asheville Plant – Field Reconnaissance,” 2014. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 11 The 2016 annual inspection, dated September 12, 2016, states that the “inspection did not identify features or conditions in the inspected ash basin dams, their outlet structures or their spillways that indicate an imminent threat of impending failure hazard. Review of critical analyses suggests the design conforms to current engineering state of practice to a degree that no immediate actions are required other than the recent and ongoing surveillance and monitoring activities already being practiced.” Summary recommendations were developed for both the 1982 and 1964 Ash Basin Dams. The recommendations are summarized in Table 3-1 and Table 3-2 for the 1982 and 1964 Ash Basin Dams, respectively. Table 3-1: 1982 Ash Basin Dam Summary Recommendations (Amec Foster Wheeler 2016b) Ref. No. Recommendations 2016 Annual Inspection Status 1982 AP- 2009-1 (EPA) Take precautions to not mow slope when wet or take necessary measures to not create ruts up and down slope. No ruts observed along slope of embankment. 1982 AP- 2009-2 (EPA) Vegetative cover needs to be established in bare areas. Bare areas noted during weekly inspections are seeded as required to establish vegetation. Bare areas were not observed during the annual inspection. 1982 AP- 2009-3 (EPA) Small animal burrows found on downstream slope should be filled with appropriate material. Animal burrows observed and filled with appropriate material as necessary. Continue monitoring 1982 AP- 2010 (NCDENR) Animals should be removed from dam and burrows repaired. Animal burrows observed and filled with appropriate material as necessary. Continue monitoring. 1982 AP- 2010-2013 (NCDENR) Monitor wet area noted about halfway up downstream slope near left abutment. No wet area noted on downstream slope. Monitoring of this area continues with weekly inspections. 1982 AP- 2012-2014 (NCDENR) Monitor wetness noted at toe on right abutment and near toe drains. No wet area noted at the toe on right abutment and near the toe drains. Monitoring of this area continues. 1982 AP- 2012-1 Plant personnel should continue to perform their monthly inspections and measurements at the weir and piezometers. The measurements at the weir should not be performed during or within about 12 hours after rainfall events. Inspections and monthly measurements are continuing. 1982 AP- 2012-2 Cut trees and bushes growing within the riprap lined upstream slope. The grass and weeds growing in this area do not need to be cut or killed. Ash excavation continues. Upper portion of upstream face has established vegetation. Vegetation should be established in lower portion of upstream face. (Note: As of December 2016, ash excavation is complete and dam decommissioning activities are in progress.) 1982 AP- 2014-1a (NCDENR) Repair rutted area along left abutment toe road. Continue to monitor and repair erosion areas as necessary. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 12 Ref. No. Recommendations 2016 Annual Inspection Status 1982 AP – 2014-1b (NCDENR) Monitor mole holes noted on downstream slope. No evidence of mole activity during inspection. 1982 AP- 2014-2 Slope protection should be implemented on the upstream face of the dam during the ash removal process. Ash excavation continues. Upper portion of upstream face has established vegetation. Vegetation should be established in lower portion of upstream face. (Note: As of December 2016, ash excavation is complete and dam decommissioning activities are in progress.) 1982 AP- 2014-4 (Stantec ASH-5) Establish grass vegetation or other erosion control measures on external slope of separator dike. Continue to monitor and establish vegetation and other erosion control measures as necessary. (Note: As of December 2016, Riprap has been added to this slope in lieu of vegetation repairs.) 1982 AP 2014-8 Monthly inspection of the dam and measurements of water elevations at the piezometers and seepage flow at the weirs should continue Inspections and measurements are continuing. Table 3-2: 1964 Ash Basin Dam Summary Recommendations (Amec Foster Wheeler 2016b) Ref. No. Recommendations 2016 Annual Inspection Status 1964 AP- 2009-2 (EPA) Establish a program to have rip-rapped slope cleared of vegetation at least once every year. Riprap slope is sprayed with herbicide as necessary to kill vegetation. 1964 AP- 2010&2011-1 (NCDENR) & 2014-1 Monitor seepage at toe of dam on right abutment where 1971 section over 1964 section begins. This area of seepage is monitored for change during monthly and weekly inspections. Observed to be similar to previous inspections. 1964 AP- 2012-1 Recommended that safety inspection of the 1964 Ash Pond Dam should continue annually. Annual inspections performed by Amec Foster Wheeler. 1964 AP- 2012-2 Regularly remove trees and bushes from the face of the dam. D/S Slope of dam is sprayed with herbicide as necessary to kill young trees and bushes. 1964 AP- 2012-4 Consider installing a flow monitoring weir at the outfall from the concrete structure that collects flow from the toe drains. Flow meters that were previously installed at toe drain outlets and flow rates are recorded monthly by Duke personnel. 1964 AP- 2014-2 Consider installing a flow monitoring device at the outfall of the corrugated HDPE culvert beneath the toe road along the right abutment to monitor seepage from the upstream area where 1971 section over 1964 section begins. In the interim, measure flow with pan and stopwatch. Flow monitoring device installed in October 2015. Flow is visually monitored and recorded during weekly inspections. Flow is collected into a two inch diameter PVC pipe and discharges into the toe drain outlet structure. 1964 AP- 2014-4 (Stantec ASH-6) Future inspections of the pipe should be performed without water flowing. (Note: this refers to Stantec’s Video inspection of the HDPE pipe installed in 2012 between MH#1 in 1964 pond and the new stilling basin outside the 1964 pond.) Future inspection videos should be performed at a 5-year interval with no flow in the pipe. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 13 Ref. No. Recommendations 2016 Annual Inspection Status 1964 AP- 2014-5 Stability analyses should be performed to improve the adequacy of supporting technical documentation. Additional analysis performed by AECOM. Based on report dated March 31, 2016, the 1964 Ash Pond Dam is stable for the static and seismic loading conditions outlined in the Duke programmatic guidelines and CCR Rules. 2015-1 Structural (Amec Foster Wheeler) The riser structure at the Duck Pond within the 1964 Ash Pond could not be evaluated due to lack of information regarding the timber pile foundation system. By inspection, we conclude that this structure was not designed for seismic events and it would likely fail under seismic loading conditions. Duke evaluating condition to determine appropriate action. 2015-2 Geotechnical (Amec Foster Wheeler) Slope Stability Analyses: The pseudo seismic acceleration must be updated to meet the requirements of the MPD. Slope stability analyses should be performed for the section at stations 10+00 (where an alluvial layer was indicated) and 13+50 for the downstream section under static and pseudo static load cases. Additional analysis performed by AECOM. Based on report dated March 31, 2016, the 1964 Ash Pond Dam is stable for the static and seismic loading conditions outlined in the Duke programmatic guidelines and CCR Rules. 2016-1 (Duke Energy weekly inspections) Small section of riprap on southern downstream slope near abutment road has bare soil. Bare soil should be covered with additional riprap. Area should be repaired in near future (Duke Work Order # 9583222-3). 2016-2 (Duke Energy weekly inspections) Northern upstream slope has areas of bare soil and erosion rills in where grading has occurred from the temporary ash stacking project. These areas shall be revegetated. Bare areas on the northern upstream slope will be revegetated in near future. 2016-3 (Duke Energy weekly inspections) Erosion along south abutment road. Erosion shall be continued to be monitored and repaired as necessary. 2016-3 (Duke Energy weekly inspections) Seepage noted on divider dike on downstream slope into the 1982 basin. The seep will continue to be monitored during weekly inspections. No flow was observed during the annual inspection. 3.2 Site Maps 3.2.1 Summary of Existing CCR Impoundment Related Structures A site map that includes a summary of the CCR impoundment-related structures is included as Figure 3. This map illustrates the following features that are associated with the CCR units:  Property boundary (determined from Buncombe County GIS);  Location of main steam Plant;  Identification of the CCR surface impoundments and their approximate boundaries;  500-foot compliance boundary for the basins (developed from SynTerra information);  Location of the existing Primary Spillway System and associated features;  Locations of the Rim Ditch and Decant Basin operations; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 14  Location of center pond filter system and associated features;  Drainage culverts downstream of the Ash Basins and under Interstate I-26. 3.2.2 Receptor Survey SynTerra completed a report, Drinking Water Well and Receptor Survey for Asheville Steam Electric Plant, September 2014 (SynTerra 2014a), and later updated it with the Supplement to Drinking Water Well and Receptor Survey for Asheville Steam Electric Plant, November 2014 (SynTerra 2014b). The receptor surveys were further updated in the CSA under Section 4.0 (SynTerra 2015a) and in the CSA Supplement 1 (SynTerra 2016b), and Receptor Information with human and ecological receptors, pathways, and their risks associated with exposure to coal ash-derived constituents that maybe present in soil, sediments, surface water, and groundwater are described in Section 5.0 of the CAP part 2 (SynTerra 2016a). Results of the two receptor surveys, and risk assessment updates from the CSA, CAP parts 1 and 2 are herein referred to collectively as receptor surveys, are summarized as follows. Completion of the receptor surveys included the collection, compilation, and assessment of electronic and field data. Publicly available electronic data used in receptor surveys includes the following sources:  NCDEQ Division of Environmental Health;  NC OneMap GeoSpatial Portal;  DWR Source Water Assessment Program online database;  County geographic information system;  Environmental Data Resources, Inc.;  USGS National Hydrography Dataset. In addition to the collection and assessment of electronic data, SynTerra completed a visual reconnaissance by driving along public roadways and obtaining information from local property owners using questionnaires. These activities were completed within an approximate 0.5-mile radius of the facility compliance boundary. The goals of these surveys were to identify land development and use, and additional potential water supply wells, including detailed well completion information when possible. The entire dataset for the receptor surveys was collected to satisfy requirements stipulated by the following:  CAMA 2014 – North Carolina S.B. 729;  Notice of Regulatory Requirements received by Duke on August 13, 2014. In addition to identification of receptors, the compiled data was used to develop a description of the site, surrounding area, geology, and hydrogeology, including a Site Hydrogeologic Conceptual Model (SCM) which are documented in Sections 4.0 and 5.0 of this document. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 15 The results of the receptor surveys conclude the following:  No public municipal water supply wells exist within the 0.5-mile radius of the compliance boundary. The closest public municipal water supply wells are more than 2 miles from the Site, and produce water from bedrock at depths between 320 to 500 feet below ground surface in areas separated from groundwater near the Asheville Plant by topographic and groundwater divides including the French Broad River;  Forty private water supply wells and 3 springs were identified within the 0.5-mile radius of the compliance boundary (Figure B-1, Appendix B). However, most of the residences receive potable water from municipal water lines, and not all private water wells have been field verified. Additionally, most of these wells are potentially isolated by topographic and groundwater divides, including being west of the French Broad River, or are upgradient of the groundwater flow direction (Figure B-1, Appendix B);  Four of the water supply wells had iron, manganese, sulfate, and TDS above 2L, and NCDEQ recommended that the associated residents use an alternate drinking water supply;  Five of the 40 private water supply wells within the 0.5-mile radius of the compliance boundary are on the east side of the French Broad River, south of the ash basin along the residential road Bear Leah Trail. A municipal water supply line was completed in 2016 (Figure B-1, Appendix B), and the existing private wells along Bear Leah Trail were abandoned in 2016 (SynTerra 2016b);  Human health exposure media includes potentially impacted groundwater, soil, surface water and sediments with exposure pathways including ingestion, inhalation and dermal contact of the exposure media;  Potential ecological receptors include aquatic (e.g., fish, benthic invertebrates), semi- aquatic (e.g., piscivorous birds and mammals), and terrestrial (e.g., terrestrial invertebrates, plants, mammals, passerine birds, raptors) receptors;  While some constituents are found in various media at greater concentrations in the source areas relative to background, many constituents that exceed screening criteria occur at naturally elevated levels. The identified public and private water supply wells are listed in Table B-3 of Appendix B. The table summarizes the following information:  Map well ID (for figures referenced within the report);  Property address;  Property owner;  Parcel ID number;  Source of drinking water; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 16  Well use;  Approximate distance from compliance boundary (feet);  Well depth (feet);  Well casing or open hole depth (feet). Six of the private water supply wells (DW-3, DW-14, DW -19, DW-27, DW-32, and DW-34) identified within the 0.5-mile radius of the compliance boundary were sampled by NCDEQ for water quality parameters and constituents, including drinking water constituents and parameters, presented in Table B-1, Appendix B, between February and July 2015. Two of the sampled wells (DW-3 and DW-19) are on the east side of the French Broad River and south of the Plant. The other four sampled wells (DW-14, DW-27, DW-32, and DW-34) are west of the French Broad River, and south and west of the Plant (Figure B-1, Appendix B). Analytical results are further discussed in the CSA. In 2016, Duke began assessing the water supply wells to understand if the concentrations reflect natural conditions or other potential source areas west of the French Broad River (such as agricultural run-off, use of pesticides, or detergents in septic tank systems). Groundwater underflow across the French Broad River would not be anticipated under natural conditions. Therefore, the assessment is focused on understanding the reason for the constituent concentrations observed (SynTerra 2016b). Duke collected additional groundwater samples from the former water supply wells on Bear Leah Trail prior to well abandonment and from water supply wells located on the west side of the French Broad River (AS-9, AS-11, AS-13, AS-14, and AS-20) using the available well pumps. Analytical results are further discussed in the CSA Supplement 1, and results are depicted on Figures 1-14, 1-20, 1-23, 1-47, and 1-50 (Appendix B). The risk assessment synopsis in Section 5.0 of part 2 of the CAP also states that media exposure estimates were less than their respective risk-based concentrations (RBCs) for current use exposure to groundwater with respect to construction and commercial worker exposure via dermal and incidental ingestion pathways. Additionally, Haley and Aldrich (2015) performed an analysis of the groundwater data collected by NCDEQ from 8 private drinking water wells located less than 0.5 miles of the Asheville facility, and 13 private drinking water wells located within a 2 to 10 mile radius of the Asheville facility that concluded the testing provided no evidence for a coal ash management unit release related impact. However, based on lowest observed adverse effect level-derived toxicity reference values, the baseline ecological risk assessment identified potential risk to wildlife from barium, manganese, molybdenum, selenium, and vanadium in seeps and seep soils within the immediate ash basin area (SynTerra 2016a). The settling pond was also identified as a potential risk to wildlife associated with selenium exposure, and in the French Broad River the selenium lowest observed adverse effect level- based HQ was 1 for the meadow vole receptor. However, SynTerra states that the food chain model for risk is an over estimate and selenium is not expected to pose unacceptable risks to ecological receptors in the French Broad River floodplain. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 17 Part 2 of the CAP, Section 2.6, also states numerous wells have been abandoned since completion of the CSA and are provided in Appendix A of Part 2 of the CAP. 3.2.3 Existing On-Site Landfills No existing on-site landfills are present at the Asheville Plant. 3.3 Monitoring and Sampling Location Plan SynTerra provided a groundwater monitoring and sampling location plan in the CSA for future monitoring. The monitoring well locations of both historical and planned sampling are shown on Figure 2-1 and Figure 16-1 of Appendix B. 3.3.1 Interim Groundwater Monitoring Plan The groundwater monitoring and sampling location plan is a longer-term, future sampling plan described under Section 16.0 of the CSA. The goals of this plan are to collect sufficient data to determine site-specific background water quality concentrations, support current interpretations of Site data, and to monitor for temporal trends. The Interim Groundwater Monitoring Plan recommends a total of 46 monitoring well locations within 5 different geologic units including (Table 16-2 and Figure 16-1, Appendix B):  Alluvium – 9 monitoring wells;  Transition Zone – 17 monitoring wells;  Saprolite – 8 monitoring wells;  Bedrock – 12 monitoring wells. The groundwater monitoring wells were also selected to include a combination of the above geologic units for groundwater monitoring in areas based on the following rationales:  Determine background concentrations upland of basins – 9 monitoring wells;  Downslope of the ash basin, both next to the French Broad River (13 monitoring wells) and southwest (8 monitoring wells) of the Site – 21 monitoring wells;  Monitor contaminant migration south (2 monitoring wells), east (2 monitoring wells), and northwest (5 monitoring wells) of the basins – 9 monitoring wells;  Next to 1964 basin, to monitor intersecting flow path to French Broad River – 7 monitoring wells. The recommended parameter and constituent list includes a set of 6 field parameters, a suite of 21 inorganic constituents, major cations and anions, nitrate, total dissolved solids (TDS), total organic carbon (TOC), and total suspended solids (Table 16-1, Appendix B). Analytical methods and associated reporting limits are also provided for each parameter and constituent (Table 16-1, Appendix B). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 18 The Interim Groundwater Monitoring Plan recommends a triannual groundwater sampling frequency intended to provide insight into potential seasonal trends, if any. The Interim Groundwater Monitoring Plan presented in Section 16.0 of the CSA described above will be superseded by the updated Interim Monitoring Plan (IMP), and a post-closure Effectiveness Monitoring Program (EMP) described in Section 9.0 of Part 2 of the CAP, if and when the proposed remedial actions are accepted as proposed in Part 2 of the CAP. The IMP and EMP proposed in Part 2 of the CAP are described in further detail under Section 11 of this document. Additional characterization of the bedrock flow system beneath the ash basins and at a background location was requested by NCDEQ (SynTerra 2016b). Monitoring well ABMW-11BR was installed at a central location within the 1964 and 1982 Ash Basin waste boundary (Figure 1-2, Appendix B). ABMW-11BR has been sampled twice since installation. Monitoring well CB- 1BRL was also installed at a background location (Figure 1-2, Appendix B). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 19 4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL INVESTIGATIONS The information in this section is a summary based on the Phase 2 Reconstitution Report (Amec Foster Wheeler 2015e), CSA report (SynTerra 2015a), and CSA Supplement 1 (SynTerra 2016b). More detailed descriptions can be found in the original reports. 4.1 Hydrogeology and Geologic Descriptions 4.1.1 Regional Geology The Plant is within the Blue Ridge Physiographic Province of North Carolina. This province is characterized by a mountainous vegetated terrain with elevations ranging from 1,500 feet above mean sea level at the base of the escarpment to summit altitudes of over 6,000 feet. The formations that underlie the Blue Ridge Physiographic Province primarily consist of complexly folded and faulted metamorphic and igneous rock with some sedimentary rock that make up the Blue Ridge geologic belt. The Blue Ridge geologic belt complexity is a result of extensive sheet thrusting, and is bounded to the southeast by the Brevard zone, a zone of major southwest–northeast faulting, and to the northwest by the Valley and Ridge Physiographic province in eastern Tennessee that are composed of low angle thrust faults. Within the Brevard zone, there are two major thrust faults approximately 1.3 miles southeast of the site (Figure 6-1, Appendix B). Since their deformation and Cenozoic uplift, this assemblage of metasedimentary and metavolcanic rock has been exposed and subjected to an extended period of erosion, and the erosion has produced a rugged terrain, consisting of steep mountains, intermittent basins, and trench valleys. 4.1.2 Regional Hydrogeology Due to the geologic complexity of the Blue Ridge Physiographic Province, numerous studies have been conducted, including the USGS Regional Aquifer-System Analysis, which refers to hydrogeologic terranes instead of identifying specific aquifers and confining units for the province. Groundwater occurrence in the Blue Ridge Physiographic Province has been grouped into two hydrogeologic terranes identified by rock types and median well yields: 1. Gneiss-granite terrane having an interquartile well yield of approximately 8 to 32 gallons per minute (gal/min); 2. Schist-sandstone terrane having an interquartile well yield of approximately 10 to 61 gal/min. Groundwater resides within the soil/saprolite regolith and is hydrologically connected with the underlying fractured bedrock forming a composite water-table aquifer system. Local groundwater flow is primarily influenced by 1) the soil/saprolite regolith thickness, and its existence, and 2) the nature of the parent bedrock. Typically, topographic highs exhibit thinner soil/saprolite zones, and topographic lows exhibit thicker soil/saprolite zones, with gneiss and Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 20 schist rock sources having thicker soils and relatively higher fracture densities compared to unaltered igneous rocks, including granite. The higher fracture density and thicker soil zones of the gneiss and schist bedrock provide efficient transition zones with less clay, and may facilitate both rapid lateral groundwater movement along unweathered bedrock and vertical groundwater movement to underlying fractured rock. Groundwater flow is also influenced in the area by precipitation serving as recharge, seasonal water table fluctuations with highs in the winter and lows in the fall, flow boundaries such as rivers, and topography where ridges can serve as groundwater divides. In general, groundwater flow in the area can be classified as a slope-aquifer system. 4.2 Stratigraphy of the Geologic Units Underlying Surface Impoundments The stratigraphy of geologic units underlying the surface impoundments is similar in characteristics described for the local and regional geology. A comparison of preconstruction topography before installation of the ash basin to current elevations is consistent with measured ash thickness in core samples and indicates ash depth generally mimics the historical land surface. Borings drilled within the ash basins indicated a distinct contact between the ash and underlying soils without visible evidence of ash staining into underlying soils (Section 7 of CSA report). In particular, the ash basins directly overly the local residual soils (Section 7 of CSA report). Toward the Lake Julian dam, ash overlies saprolite with increasing thickness (Figure 6-3 and Figure 6-4, Appendix B). The saprolite within the ash basin is underlain by transition zone media and a bedrock of mica gneiss, a member of the late Precambrian Ashe Metamorphic Suite. The Geologic Map of the Skyland Quadrangle (Dabbagh 1981) describes the underlying bedrock as being mainly composed of gray to dark gray, fine- to medium-grained gneiss. Of note is a shear zone trending northeast-southwest, which is mapped to underlie the approximate northwestern side of the 1982 Ash Basin. 4.3 Hydraulic Conductivity Information The horizontal hydraulic conductivities of the site hydrogeologic zones were determined from in- situ field slug testing of wells in accordance with the Groundwater Assessment Work Plan (GAP) Section 7.1.4 (Table 6-5, Appendix B). The slug tests were performed in accordance with the documented standard ASTM D4044-96 (Appendix C of CSA report [SynTerra 2015a]). A total of 143 slug tests was performed at 47 well locations (Table 4-1). The tests were analyzed primarily by the Hvorslev analytical solution, with some well tests analyzed by the Bouwer-Rice analytical solution for wells that were not fully penetrating (Appendix G of CSA report [SynTerra 2015a]) according to the methodology described in Appendix C of the CSA report. Locations of tested wells are shown on Figure 2-1 of Appendix B. The slug testing results listed in Table 6-5 of Appendix B includes individual well test hydraulic conductivity results, calculated geometric means for repeated testing of individual wells and for each hydrogeologic zone having multiple well results, and minimum and maximum values for Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 21 individual wells and for each hydrogeologic zone. Testing results include testing of wells completed in hydrogeologic zones below the ash basins and in the surrounding area (Figure 2- 1, Appendix B). Table 4-1: Summary of Hydraulic Conductivity Geometric Mean Monitoring Well Slug Testing Results for Each Hydrogeologic Zone Hydrogeologic Zone Number of Wells Tested Number of Slug Tests Hydraulic Conductivity Geometric Mean (cm/sec) Hydraulic Conductivity Geometric Mean (ft/day) Ash Basins 3 7 1.52E-04 4.32E-01 Alluvium 2 15 3.21E-03 9.09E+00 Saprolite 7 25 2.83E-04 8.01E-01 Transition Zone 18 57 3.09E-04 8.76E-01 Bedrock 17 39 4.77E-04 1.35E+00 The results of slug testing indicate spatial variability throughout the site and between different hydrogeologic zones. Slug testing of alluvial deposits indicated approximately an order of magnitude higher hydraulic conductivity than other hydrogeologic zones (Table 4-1). The hydraulic conductivity values for wells screened in the transition zone spanned three orders of magnitude from 1.1 × 10E-5 to 1.3 × 10E-2 centimeters per second (cm/sec), with a mean of 3.1 × 10E-4 cm/sec (Table 6-5, Appendix B). The large range in results reflects the degree of weathering which can be highly variable within the transition zone and related to the degree of infilling of fractures, varying amounts of clays, and other weathering products. In addition to in-situ, horizontal hydraulic conductivity slug testing, three laboratory vertical hydraulic conductivity tests were performed on cores collected in Shelby tubes. These laboratory tests are reflective of site conditions because the ash basin is not lined (Table 6-6, Appendix B). A 2.5-foot core was collected from bore hole ABMW-02SB, and 2-foot cores were collected from both ABMW-07 and MW-16SB (Table 6-6, Appendix B). The intervals selected for testing the core represent three distinct zones: saprolite, ash, and alluvium, with values of 2.60E-06, 8.60E-06, and 4.80E-07 cm/sec, respectively. The vertical conductivity testing results are one to two orders of magnitude lower than horizontal conductivity values from in-situ slug testing, supporting a predominantly lateral groundwater flow in the Site area. In addition, the results support a predominantly lateral migration of COIs relative to vertical migration. 4.4 Geotechnical Properties Subsurface investigations were performed as part of previous design and reconstitution projects at the Asheville Steam Electric Generating Plant. A summary of available boring, monitoring Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 22 well, and piezometer locations involving the ash basins is shown on Figure 4. In these investigations, geotechnical properties were developed to characterize the soils and ash present at the site. As previously discussed, there is no liner underneath the ash basins. For this Removal Plan, the geotechnical properties listed below were gathered from the following previous reports:  Amec Foster Wheeler, “Subsurface Exploration and Laboratory Testing Data Report, Landfill Development and Ash Basin Closure,” August 2015;  Amec Foster Wheeler, “Phase 2 Reconstitution of Ash Pond Designs, Final Report Submittal, Revision B, Asheville Steam Station,” July 17, 2015;  S&ME, Inc., “Subsurface Investigation and Slope Stability Analysis of 1964 Ash Basin Dike,” December 28, 2009;  S&ME, Inc. “1964 Ash Basin Dam Improvement Design – Appendix I – Slope Stability Analysis Discussion and Summary,” December 28, 2009;  MACTEC Engineering and Consulting, Inc., “Geotechnical Exploration Data Report, Asheville FGD Project, Constructed Wetlands System,” October 18, 2004;  MACTEC Engineering and Consulting, Inc., “Report of Geotechnical Exploration, 1982/1964 Ash Pond Drainage Modification Project,” January 19, 2011;  MACTEC Engineering and Consulting, Inc., “Final Report for Task ASH-1 Issue,” August 2014;  Law Engineering, Inc., “Stability Analysis of Downstream Slope, 1982 Ash Pond Dike,” September 30, 1992;  AMEC, “Asheville Steam Plant, Final Report for Task ASH-2 Issue,” August 26, 2014. 1982 Ash Basin Dam Design parameters for the 1982 Ash Basin Dam were developed from the analysis completed by Law Engineering (1992) and from the Phase 2 Reconstitution of Design report (Amec Foster Wheeler 2015e). The following material properties were developed from these analyses: Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 23 Table 4-2: Unit Weight and Shear Strength Parameters for the 1982 Ash Basin Dam Material Description Unit Weight Shear Strength Effective R-Envelope (pcf) c’ (psf) Ф’ (degree) c’ (psf) Ф’ (degree) Embankment 120 400 33.9 0 32.8 Sand Drain 120 0 36 0 36 Foundation Soil 130 400 32 650 30 Partially Weathered Rock 135 10,000 45 10,000 45 *Note: Material Description information is included in the Phase 2 Reconstitution Report (Amec Foster Wheeler 2015e). 1964 Ash Basin Dam The subsurface stratigraphy for the dam has been based on the stability analysis completed for the 1964 Ash Pond Dam (S&ME 2009) and on the Phase 2 Reconstitution of Design report (Amec Foster Wheeler 2015e). The following material properties were developed from this analysis: Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 24 Table 4-3: Unit Weight and Shear Strength Parameters for the 1964 Ash Basin Dam Material Description Unit Weight Shear Strength Effective R-Envelope (pcf) c’ (psf) Ф’ (degree) c’ (psf) Ф’ (degree) Zone 1 - Core 120 200 32 600 17 Zone 2 - Rock Shell 120 0 47 0 47 Zone 3 – Mixed Fill 120 0 40 440 24 Zone 4 – Drainage Zone 120 0 36 0 36 Upstream Rockfill 120 0 40 0 40 Ash Fill 120 0 30 0 30 Ash (Above Water) 85 0 30 0 30 Ash (Below Water) 85 0 30 0 20 Ash Stack 85 0 30 0 30 Original 1964 Dike Fill 120 0 40 420 21 1971 Cofferdam Fill 120 0 30 300 20 Stilling Pond Embankment 120 140 33 400 20 Alluvium 120 50 28 50 24 Residual Soil 120 115 35 330 25 Partially Weathered Rock 120 1000 40 1000 40 *Note: Zone and Material Description information is included in the Phase 2 Reconstitution Report (Amec Foster Wheeler 2015e) Separator Dike The design parameters for the Separator Dike were developed from the Final Report for Task ASH-2 Issue (AMEC 2014b) and from the Phase 2 Reconstitution of Design report (Amec Foster Wheeler 2015e). The following material properties were developed from these analyses: Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 25 Table 4-4: Unit Weight and Shear Strength Parameters for the Separator Dike Material Description Unit Weight Shear Strength Effective R-Envelope (pcf) c’ (psf) Ф’ (degree) c’ (psf) Ф’ (degree) Embankment 120 400 33.9 0 32.8 Zone 3 120 0 40 435 24.4 Ash 85 210 28.8 40 19.4 Zone 1 120 200 32 1000 16.9 Foundation Soil 130 400 32 650 30 Partially Weathered Rock 135 10,000 45 10,000 45 *Note: Zone and Material Description information is included in the Phase 2 Reconstitution Report (Amec Foster Wheeler 2015e). Residual Materials in 1982 Ash Basin Amec Foster Wheeler drilled an additional 30 borings within the limits of the 1982 Ash Basin. Laboratory tests were performed on samples collected from these borings. The samples generally consisted of ash fill within the basin, and residual materials from the original ground underlying the basin. Since ash removal was completed on September 30, 2016, Table 4-5 only lists the material properties that were developed for the residual materials from these analyses. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 26 TABLE 4-5 Index Property Test Results of Materials in 1982 Ash Basin Boring Sample Type Sample Depth (Feet bgs) Visual Identification Natural Moisture Content, % Dry Unit Weight, pcf Atterberg Limits Percent Finer Than No. 200 Sieve Other Test Liquid Limit Plastic Limit Plasticity Index BL-1A UD-1 15-17 Yellowish Brown Silt with Sand (ML)- RESIDUUM 74.8* 81.6* NP NP NP 82.8 S.G. = 3.00 k BL-8 Bulk-1 0-10 Brown Silty Sand (SM) - RESIDUUM 22.7* NP NP NP 41.1 S.G. = 2.72 P BL-14 Bulk-1 0-8.9 Brown Silty Sand (SM) - RESIDUUM 12.9 12.7* NP NP NP 27.7 S.G. = 2.78 P BL-19 Bulk-1 0-10 Brown Silty Sand (SM) - RESIDUUM 17.8 NP NP NP 36.2 S.G. = 2.73 P SPT-Standard Penetration Test/Split-Spoon; UD-Undisturbed Sample; Prepared/Date: H. Benkhayal/7-29-2015 P - Moisture-Density Relationship Test; NP-Non Plastic; Checked/Date: C. Tockstein/7-29-2015 k – Hydraulic Conductivity Test; S.G.-Specific Gravity Test *Result obtained from a different laboratory test method (i.e., Hydraulic Conductivity, Atterberg limit test, etc.) Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 27 CCR and Residual Materials in 1964 Ash Basin A subsurface investigation was performed by Amec Foster Wheeler in 2015 with the intent of providing additional information for the development of closure and/or landfill options for the ash basins. As part of this investigation, 10 borings were drilled within the limits of the 1964 Ash Basin. Laboratory tests were performed on samples collected from these borings. The samples generally consisted of ash fill within the basin, and residual materials from the orig inal ground underlying the basin. The following material properties were developed from these analyses: Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 28 TABLE 4-6 Index Property Test Results of Materials in 1964 Ash Basin Boring Sample Type Sample Depth (Feet bgs) Visual Identification Natural Moisture Content, % Dry Unit Weight, pcf Atterberg Limits Percent Finer Than No. 200 Sieve Other Test Liquid Limit Plastic Limit Plasticity Index BC-2 UD-1 21-23 Dark Gray Sandy Silt (ML) - Fly Ash - FILL 26.7* NP NP NP 55.4 S.G. = 2.15 BC-2 UD-2 51-53 Brown Micaceous Silty Sand (SM) - RESIDUUM 18.5* 20.5* NP NP NP 13.7 S.G. = 2.81 k BC-4 SPT-1 3.5-5 Light to Dark Gray Sandy Silt - Fly Ash - FILL 35.5 BC-4 SPT-2 8.5-10 Light to Dark Gray Sandy Silt - Fly Ash - FILL 35.4 BC-4 SPT-3 13.5-15 Dark Gray Sandy Silt - Fly Ash - FILL 34.3 BC-4 SPT-4 18.5-20 Dark Gray Sandy Silt - Fly Ash - FILL 40.9 BC-4 SPT-6 28.5-30 Dark Gray Sandy Silt - Fly Ash - FILL 47.0 BC-4 SPT-8 40-41.5 Dark Gray Sandy Silt - Fly Ash - FILL 46.8 BC-4 SPT-10 48.5-50 Dark Gray Sandy Silt - Fly Ash - FILL 45.5 BC-4 SPT-12 58.5-60 Dark Gray Silty Sand with Gravel - Fly Ash - FILL 38.4 BC-4 SPT-14A 68.5-69.2 Light to Dark Gray Sandy Silt - Fly Ash - FILL 37.7 BC-4 SPT-14A 69.2-70 Reddish Brown Sandy Lean Clay - RESIDUUM 24.8 BC-4 SPT-16 78.5-79 Dark Gray and Brown Silty Sand - RESIDUUM 29.8 SPT-Standard Penetration Test/Split-Spoon; UD-Undisturbed Sample; Prepared/Date: H. Benkhayal/7-29-2015 P – Moisture-Density Relationship Test; NP-Non Plastic; k – Hydraulic Conductivity Test; Checked/Date: C. Tockstein/7-29-2015 S.G.-Specific Gravity Test *Result obtained from a different laboratory test method (i.e. Hydraulic Conductivity, Atterberg limit t est, etc.) Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 29 TABLE 4-6 (Continued) Index Property Test Results of Materials in 1964 Ash Basin Boring Sample Type Sample Depth (Feet bgs) Visual Identification Natural Moisture Content, % Dry Unit Weight, pcf Atterberg Limits Percent Finer Than No. 200 Sieve Other Test Liquid Limit Plastic Limit Plasticity Index BC-4 UD-1 20-22 Dark Gray Silty Sand (SM) - Fly Ash - FILL 18.0* NP NP NP 43.8 S.G. = 2.34 BC-5 Bulk-1 28.5-38.5 Dark Gray Silt with Sand (ML) -Fly Ash - FILL 31.3* NP NP NP 80.5 S.G. = 2.26 P BC-7 Bulk-1 5-15 Dark Gray Silt (ML) - Fly Ash - FILL 25.6* NP NP NP 84.8 S.G. = 2.34 P BC-8 UD-1 26-28 Reddish Brown Silty Sand (SM) - RESIDUUM 14.8* NP NP NP 30.1 S.G. = 2.73 k BC-8 UD-2 55.5-57.5 Gray Micaceous Silty Sand (SM) - RESIDUUM 27.5* 32.5* NP NP NP 25.3 S.G. = 2.80 k BC-9 SPT-1 5-6.5 Very Dark Gray Sandy Silt – Fly Ash - FILL 32.4 BC-9 SPT-2 8.5-10 Very Dark Gray Sandy Silt – Fly Ash - FILL 42.2 BC-9 SPT-3 13.5-15 Very Dark Gray Sandy Silt – Fly Ash - FILL 39.3 BC-9 SPT-4 18.5-20 Very Dark Gray Sandy Silt – Fly Ash - FILL 32.5 BC-9 SPT-5 23.5-25 Very Dark Gray Sandy Silt – Fly Ash - FILL 51.9 BC-9 SPT-6 28.5-30 Very Dark Gray Sandy Silt – Fly Ash - FILL 43.6 BC-9 SPT-7 33.5-35 Very Dark Gray Sandy Silt – Fly Ash - FILL 58.1 SPT-Standard Penetration Test/Split-Spoon; UD-Undisturbed Sample; Prepared/Date: H. Benkhayal/7-29-2015 P - Moisture-Density Relationship Test; NP-Non Plastic; k – Hydraulic Conductivity Test; Checked/Date: C. Tockstein/7-29-2015 S.G.-Specific Gravity Test *Result obtained from a different laboratory test method (i.e. Hydraulic Conductivity, Atterberg limit test, etc. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 30 TABLE 4-6 (Continued) Index Property Test Results of Materials in 1964 Ash Basin Boring Sample Type Sample Depth (Feet bgs) Visual Identification Natural Moisture Content, % Dry Unit Weight, pcf Atterberg Limits Percent Finer Than No. 200 Sieve Other Test BC-9 SPT-9 43.5-45 Very Dark Gray Sandy Silt – Fly Ash - FILL 78.5 BC-9 SPT-11 53.5-55 Strong Brown, Yellow, and Dark Reddish Brown Sandy Silt - RESIDUUM 23.4 BC-9 SPT-13 63.5-65 White, Strong Brown, and Very Dark Gray Sandy Silt - RESIDUUM 40.7 BC-10 Bulk-1 13.5-23.5 Dark Gray Silt (ML) - Fly Ash - FILL 27.9* NP NP NP 86.1 S.G. = 2.30 P BC-10 UD-1 35-37 Gray Silt (ML) - Fly Ash - FILL 26.8* NP NP NP 97.8 S.G. = 2.31 SPT-Standard Penetration Test/Split-Spoon; UD-Undisturbed Sample; Prepared/Date: H. Benkhayal/7-29-2015 P - Moisture-Density Relationship Test; NP-Non Plastic; k – Hydraulic Conductivity Test; Checked/Date: C. Tockstein/7-29-2015 S.G.-Specific Gravity Test *Result obtained from a different laboratory test method (i.e. Hydraulic Conductivity, Atterberg limit test, etc.) Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 31 4.5 Chemical Analysis of Impoundment Water, CCR Materials and CCR Affected Soil Source area characterization of the site is described in the CSA (SynTerra 2015a) and supplemented by the CAP Part 1 (SynTerra 2015b). The characterization includes the collection and analysis of soil, groundwater, surface water, and sediment samples from the ash basins and surrounding area to identify provisional background concentrations and the extent of impacts. Sample locations are identified on Figure 2-1, Appendix B. Development of groundwater provisional background concentrations for key constituents is an ongoing process that primarily entails collection of sufficient groundwater samples to provide statistically meaningful results. The long-term goal is to calculate upper prediction limits for the pool of background data to be used for comparison to samples collected from monitoring wells located hydraulically downgradient of the ash basins. EPA guidance documents indicate that eight to 10 rounds of background sample data are necessary to develop meaningful provisional background concentrations. Six rounds of background sample data are included in the CSA Supplement 1 (SynTerra 2016b), and results are tabulated in Tables 4-1 through 4-8 (Appendix B).The analysis of CCR ash and pore water from the ash basins resulted in the identification of Site- specific constituents of interest (COIs). The COls are constituents that are associated with the ash basin and are elevated above background values. Some COIs are also identified in water quality samples collected from background monitoring wells, and they require careful examination to determine their origin and source. The COIs identified from the Asheville Plant ash material and pore water sample analyses include antimony, arsenic, boron, chromium, cobalt, iron, manganese, sulfate, thallium, TDS, vanadium, and pH. These COIs are identified as exceeding either the 2L or Interim Maximum Allowable Concentrations (IMAC) in at least one ash pore water monitoring well (CSA report [SynTerra 2015a]). 4.5.1 Source Area(s) Characterization Included in this section are the results of the ash basin and seep source area characterization, as presented in the CSA Report (SynTerra 2015a). Media sampled by SynTerra included ash matrix, ash porewater, settling basin surface water, and seep water. CCR Ash Materials Chemical Analyses Results A total of 10 borings and 13 monitoring wells were drilled and installed using rotary sonic drilling with continuous sample recovery (Section 7 of CSA report [SynTerra 2015a]). The drilling locations were divided between the 1964 (borings AB-01 and AB-03 and monitoring wells ABMW-02, ABMW-02S, ABMW-04, ABMW-04D, and ABMW-04BR) and the 1982 (borings AB-09 and AB-10 and monitoring wells ABMW-05S, ABMW-05D, ABMW-05BR, ABMW-06BR, ABMW-07, ABMW-07S, ABMW-07BR and ABMW-08) ash basins (Appendix E of the CSA report). During this drilling program, ash samples were collected from the basin in accordance with GAP Section 7.1.1 for analysis of total metals, U.S. Environmental Protection Agency (USEPA) Synthetic Precipitation Leaching Procedure (SPLP), and Energy Dispersive X-Ray Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 32 Fluorescence (EDXRF) with documented methodologies in Appendix C of the CSA report (SynTerra 2015a). Results from 16 ash samples were analyzed for total metals, and results identified 14 constituents (aluminum, antimony, arsenic, barium, beryllium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, selenium, and vanadium) at levels exceeding one or more of the USEPA Soil Regional Screening Level (Table 7-4, Appendix B). Ash samples from the basin were also analyzed for TOC content and resulted in values from 9,630 to 87,800 milligrams per kilogram. Results from eight ash samples tested using the SPLP method were compared to the 2L for informational purposes and values of antimony, arsenic, chromium, cobalt, iron, manganese, nitrate, selenium, thallium, and vanadium were typically in exceedance of the 2L reference values. However, boron in ash SPLP leachate was not in exceedance of the 2L value. These results were also compared to background soil values. The comparison of ash SPLP leachate results to background soil values indicates the following:  Antimony, arsenic, selenium, and vanadium values in SPLP leachate from ash are higher than background soils. However, these metals are typically not detected in background soils, with the exception of vanadium and sporadic selenium.  Boron, chromium, cobalt, iron, lead, manganese, nitrate, and thallium leachate results indicate similar ranges of concentrations from soils and ash. While the above metals are identified as being elevated in the SPLP leachate of ash samples, SPLP concentrations in soil samples collected from below the ash basins do not suggest migration of these metals from the source material. Results from three ash samples analyzed by EDXRF indicate whole rock metal oxide (Table 7- 6, Appendix B) and elemental content (Table 7-7, Appendix B). The results indicate the ash primarily consists of oxides of silicon (SiO2), aluminum (Al2O3), and iron (Fe2O3) (Figure 7-1, Appendix B). Results from chemical analyses of ash samples collected throughout the ash basins indicate aluminum, arsenic, barium, cobalt, iron, lead, manganese, mercury, selenium, and vanadium are above either the USEPA Regional Screening Level (RSL) for Protection of Groundwater or Residential Health. CCR Ash Impoundment Pore Water Chemical Analyses Results Ash pore water quality samples were collected for analysis of the expanded analyte list, metals speciation, and radiological parameters. The samples were collected from ash basin monitoring wells ABMW-02 and ABMW-04 in the 1964 Ash Basin (Table 7-8, Appendix B), and from monitoring wells ABMW-08, P-100, P-101, and P-103 in the 1982 Ash Basin. The results indicate that antimony, arsenic, boron, chromium, cobalt, iron, manganese, sulfate, thallium, TDS, vanadium, and pH are above the 2L or IMAC in ash pore water (Table 7-9, Appendix B). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 33 Analysis of the analytical results using published methods referenced in the CSA also indicate that the redox state of pore water within both the ash basins is anoxic, with some mixed anoxic processes identified at well ABMW-04 in the 1964 basin (Table 7-8, Appendix B). Speciation results of arsenic, chromium, iron, manganese, and selenium are provided for wells ABMW-02 and ABMW-04 (Table 7-10, Appendix B). The results indicate that trivalent iron is the predominant species of iron in both well pore water samples, and hexavalent chromium is below the USEPA tapwater screening level of 0.035 microgram per liter (µg/L) in ash pore water. Settling Basin Surface Water Characteristics One surface water sample was collected from the settling basin located within the 1964 Ash Basin, SW-05 (Table 9-3, Appendix B) [SynTerra 2015a]. Most of the constituent detections above the 2L or 2B values were from this sample. SynTerra noted no corrective action is necessary because the wastewater from this basin is under a NPDES permit. Summary of CCR Waste Boundary Seep Water Sediment Characteristics Seeps have been documented and sampled by SynTerra (Figure 2-1, Appendix B). Seep data includes results from the June 2014 Asheville Seep Monitoring Report (SynTerra 2014c) with samples from 17 representative seeps below (downgradient of) the ash basins, NCDENR seep sampling in 2014 (Table 9-4, Appendix B), and seep results from 11 seeps that confirm the extent of impacted groundwater with COI values above the 2L or IMAC (Table 9-2, Appendix B). Concentrations from seep P-01 are consistent with background surface waters (Figures 9-1 and 9-2, Appendix B). SynTerra also compared the results of the 11 seep samples in Table 9- 2, Appendix B, to North Carolina Administrative Code (NCAC) Surface Water (2B) values. 4.5.2 Surface Water and Sediment Assessment Summary of Surface Water Characteristics Samples of sediment, surface water, and seeps were collected in August 2015 and analyzed for water quality (Figure 2-1, Appendix B). Sediment samples were collected from the same locations of surface water and seep sample water quality collection (Figure 2-1, Appendix B). Sediment sample results from background locations exceed one or more RSLs for a few COIs including aluminum, cobalt, iron, and manganese (Table 9-1, Appendix B). The sediment samples collected from seeps below (downgradient of) the ash basins exceeded the RSL for COIs including aluminum, antimony, arsenic, barium, cobalt, copper, iron, manganese, mercury, molybdenum, nickel, selenium, and thallium in at least one sample. The side-gradient sediment sample results from SW-01 are generally similar to background values except for elevated aluminum and barium. SynTerra provided results for surface water samples collected from the French Broad River (upstream and downstream from the Site), Lake Julian, and areas within the French Broad River floodplain. Two samples, one from upstream of the French Broad River (FB-01) and the other from Lake Julian (SW-06), serve as background locations for comparison. Surface water sample results to seep sample results are compared in Piper diagrams (Figures 9-1 and 9-2, Appendix Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 34 B). The upstream and downstream French Broad River samples did not vary. However, thallium was detected only at the upstream site (0.202 µg/L), which may indicate other potential sources of thallium outside the ash basins. The surface water samples that have concentrations greater than 2B values are listed in Table 9-5, Appendix B. Surface water sample results for constituents that are elevated compared to background and lack a 2B value include boron, iron, manganese, sulfate, TDS, and vanadium. In part 2 of the CAP, Section 2.5, SynTerra reports that additional seep, surface water, and sediment data was collected in November 2015 with a seep inspection performed on November 19, 2015. The results of an initial screening of the data indicates no substantial variation from August 2015 with no newly identified seeps. To further refine knowledge of hydrogeologic conditions, ten stream gauges were installed in March 2016. Gauges were co-located with CSA surface water sample locations A-01, A-02, B- 01, C-01, and D-01, spanning the eastern side of the French Broad River along the western stretch of the property boundary. Gauges were also co-located at SD-01 and N-01, representing the western portion of Powell Creek below the Lake Julian dam. A gauge was placed in the outfall area of the 1964 dam, correlating to surface water sample location C-02. Stream gauge survey information is provided in Table 1-1 (Appendix B). Four surface water features (two springs and two surface water drainages) were sampled as part of the additional assessment west of the French Broad River (SynTerra 2016b). The purpose of collecting surface water samples is to evaluate the contribution of agricultural and domestic activities to observed concentrations of boron in water supply wells. The primary area targeted for investigation is located on the same parcel as AS-14 (115 Justin Trail). In May 2016, four surface water samples were collected in upgradient, sidegradient, and downgradient areas to agricultural fields. Data is presented in Table 3-1 (Appendix B). 4.6 Historical Groundwater Sampling Results A detailed description of groundwater characterization from the installation and sampling of 47 new monitoring wells and 36 existing monitoring wells is provided in Section 10 of CSA report (SynTerra 2015a). A summary of those findings is provided in this section. The sampling locations and dates are listed in Table 10-1 of Appendix B, and the full parameter list with analytical methods and reporting limits are listed in Table 10-2 of Appendix B. Analytical results are listed in Table 10-3 of Appendix B. The results of groundwater sampling indicate that 18 analytes exceed the 2L or IMAC in groundwater at the Site (Table 10-4, Appendix B). The area of groundwater concentrations exceeding 2L is identified under the ash basins and to the west along groundwater flow lines up to the French Broad River (Figure ES-1, Appendix B). Five of the 18 parameters (pH, cobalt, iron, manganese, and vanadium) exceed the 2L or IMAC in one or more background wells. In 2013, chromium was sporadically detected above the 2L limit at background monitoring well CB- 01. While concentrations for 18 parameters are in exceedance of 2L or IMAC values, no private or public wells are within the impacted area (Figures ES-1, and 10-5 to 10-56, Appendix B). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 35 The speciation data results are presented in Table 10-3 of Appendix B and indicate the following:  Background groundwater is oxic, with oxic and mixed conditions in groundwater upgradient of the ash basins.  Groundwater beneath the ash basins is anoxic and mixed anoxic.  Downgradient and side gradient groundwater is variable. Part 2 of the CAP, Section 2.6, discusses additional characterization of the bedrock flow system beneath the ash basins at a background location is included within data gap activities as requested by NCDEQ. The information collected during the data gap activities is not expected to substantially alter the groundwater corrective action plans proposed in Part 2 of the CAP. The data gap activities include confirmation sampling on a private water supply well located on the west side of the French Broad River, and confirmed initial results of iron, manganese, and TDS at levels greater than the 2L standard, and boron elevated above background but below the 2L standard. Additionally, a third and fourth set of CSA groundwater data was collected in December 2015 and January 2016 for comparison to the initial two sets of data and to supplement background data. Six rounds of monitoring for CSA parameters have been completed through July 2016 and Tables 1-2 through 1-5 (Appendix B) provide a summary of groundwater from all sampling events completed to date (e.g., CSA and NPDES programs) that exceed 2L or IMAC for each of the primary hydrogeologic flow zones (surficial transition zone, and bedrock). Additional sampling is scheduled in September and November of 2016 from select Asheville wells (Table 1-8, Appendix B). Additional data from sampling results and results of analysis are included in the CSA Supplement 1 (SynTerra, 2016b). CAMA sampling locations are summarized in Table 1-8 (Appendix B) with locations and rationale for inclusion. Background wells CB-09 (saprolite), CB-09SL (lower saprolite), CB-09BR (bedrock), CB-01 (surficial), CB-01D (transition zone), AMW-03B (bedrock), and MW-10 (alluvial) are planned to be monitored to provide a more robust data set for provisional background concentration evaluation. Groundwater data reported from previous rounds of monitoring from the majority of wells across the site is consistent and confirms the current understanding of site conditions, specifically the extent of impact to groundwater from ash basin-sourced constituents (e.g., boron). However, monitoring of select wells along the east side of the French Broad River and west of the ash basins is anticipated to be ongoing in 2016. Data gap wells installed in 2016 (ABMW-11BR, MW-18BRL) are also included in the 2016 sampling program. 4.6.1 Summary of Surficial Aquifer Results Surficial aquifer samples were collected from 27 saprolite monitoring wells and 9 alluvial monitoring wells. The results indicate that impacts downgradient of the ash basins and wastewater treatment constructed wetlands from leaching of the source areas are migrating toward the French Broad River resulting in 17 parameters in the saprolite, and 11 parameters in the alluvium that exceed 2L or IMAC (Table 10-4, Appendix B). SynTerra reports that the wells completed within the surficial zone downgradient of the ash basin and the wastewater treatment Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 36 constructed wetlands are the most impacted by leaching from the source areas. The CSA Supplement 1 reports the following results for background data. Surficial groundwater is represented by alluvial well MW-10 and saprolite wells CB-1, CB-09, CB-9SL, and MW-24S, and provisional background concentrations were calculated for those wells. Exceedances above 2L and IMAC values were noted for pH (all wells), hexavalent chromium (MW -10, CB-9, CB- 9SL, and MW-24S); chromium (CB-1), cobalt (MW-10, CB-1, CB-9. MW-24S), iron (all wells), manganese (MW-10, CB-1, CB-9, MW-24S), and vanadium (CB-9). The CSA Supplement 1 reports the following results for downgradient wells. Concentrations of boron, cadmium, chloride, cobalt, iron, manganese, hexavalent chromium, selenium, strontium, sulfate, thallium, TDS, and vanadium have been detected in alluvial monitoring wells in excess of the 2L, IMAC values. In general, concentrations within the floodplain area of the French Broad River have remained relatively stable, with one exception at CB-6. Concentrations of cobalt, manganese, sulfate and TDS increased substantially between July and November 2015, January 2016, and April 2016. These increases can be correlated to a decrease in pH from 5.9 to 3.4. The pH at CB-6 was 4.7 in July 2016. Concentrations of antimony, boron, cobalt, hexavalent chromium, iron, manganese, nitrate, sulfate, TDS, thallium, and vanadium have been detected in saprolite monitoring wells in excess of the 2L and IMAC values; however, none of these constituents exceeded corresponding provisional background concentrations beyond the compliance boundary. In general, concentrations within saprolite wells have remained stable with slight increases of boron noted in wells MW-8S and MW-9S and slight increases of boron, sulfate, and TDS in GW-3. Figure 1-81 (Appendix B) presents a piper diagram that indicates samples from the alluvial and saprolite flow zones appear to be divided into two sub-groups, sulfate and chloride type. Samples collected downgradient of the 1964 Ash Basin are dominated by chloride, while those collected downgradient from the 1982 Ash Basin are more associated with sulfate type water. This difference is attributed to the former wetland treatment areas recently removed from the 1964 Ash Basin. 4.6.2 Summary of Transitional Zone Aquifer Results In general, the distribution of parameters in exceedance of the 2L or IMAC in the transition zone samples mimics those identified in the surficial aquifer, but at reduced concentrations. Twenty- four wells within the transition zone were sampled, and boron, chromium, cobalt, iron, manganese, nickel, nitrate, selenium, sulfate, thallium, TDS, and vanadium were detected at concentrations greater than the 2L or IMAC. One well, MW -09D, showed concentrations of chloride and selenium greater than the 2L. The CSA Supplement 1 reports transition zone groundwater is represented by one monitoring well, CB-1, and provisional background concentrations were determined for this well. Exceedances above 2L or IMAC are noted for pH, cobalt, iron, manganese, and vanadium. Downgradient results indicate concentrations of boron, chloride, chromium, cobalt, hexavalent chromium, iron, manganese, nitrate, nickel, selenium, sulfate, TDS, thallium, and vanadium have been detected in transition zone monitoring wells in excess of 2L and IMAC values. Of these constituents, cobalt, iron, manganese, and vanadium are detected greater than Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 37 provisional background concentrations (which are greater that the 2L or IMAC values) downgradient of the 1964 and 1982 Ash Basins beyond the compliance boundary in transition zone wells. Concentrations of boron, chloride, sulfate, and TDS beyond the compliance boundary are greater than provisional background concentrations, but less than 2L. In general, concentrations within transition zone wells have remained stable. Figure 1-82 (Appendix B) presents a piper diagram that indicates samples from the transitional flow zone associated with the 1982 Ash Basin tend to show sulfate type characteristics, while those associated with the 1964 Ash Basin tend to be associated with chloride type water. Groundwater from background locations and unaffected areas near each ash basin are characterized by calcium bicarbonate type groundwater, typical of shallow fresh groundwater. 4.6.3 Summary of Bedrock Aquifer Results Bedrock groundwater samples were collected from 20 wells and indicated exceedances of 2L or IMAC for 9 parameters, and most have exceedances of cobalt, iron, manganese, and vanadium (Table 10-4, Appendix B). Boron was only detected in a quarter of the bedrock wells sampled, and sulfate was detected above the 2L at MW-18BR. The CSA Supplement 1 presents data from two background monitoring wells, CB-9BR and AMW-3B, and provisional background concentrations were determined for these wells. Exceedances above 2L and IMAC values were noted for pH (both wells); hexavalent chromium (both wells), iron (both wells); manganese (both wells); and vanadium (both wells). Concentrations of boron, chloride, chromium, cobalt, hexavalent chromium, iron, manganese, selenium, sulfate, TDS, thallium, and vanadium have been detected in bedrock monitoring wells in excess of 2L or IMAC values. Iron and manganese have been detected in exceedance of 2L and provisional background concentrations beyond the compliance boundary to the south of the 1982 Ash Basin. Chloride, strontium, and TDS are found at levels greater than the provisional background concentration beyond the compliance boundary west of the 1964 Ash Basin and south of the 1982 Ash Basin. In general, concentrations within bedrock wells have remained stable with a few exceptions. Initial monitoring indicates increasing concentrations are noted in downgradient monitoring wells of the 1964 Ash Basin: MW-9BR (boron, chloride, iron, manganese, sulfate, strontium, and TDS) and GW-2 (boron chromium, iron, manganese, sulfate, and strontium). However, these data sets are limited, and further monitoring will determine if these increases are trends. Similar to the transition zone, bedrock groundwater is consistent with calcium-bicarbonate type water. The distinction of the 1964 Ash Basin groundwater (chloride-type) and the 1982 Ash Basin groundwater (sulfate type) is evident and most clearly defined in this flow zone. Groundwater downgradient of the ash basins is characteristic of calcium – sulfate type water (Figure 1-83, Appendix B). 4.7 Groundwater Potentiometric Contour Maps Existing site wells and piezometers have been used to monitor groundwater levels in and around the 1982 and 1964 Ash Basins. During monthly site visits, the wells and piezometers are gauged using a water-level meter to measure the depth to water to the nearest 0.01 foot. All Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 38 measurements are referenced to the top of riser casing and recorded on a well gauging form. Groundwater gauging data from June 2015 were used to develop surficial (alluvium, saprolite, and transition zone) and bedrock water-level maps (Figure 6-10 and Figure 6-11, respectively, Appendix B). And groundwater gauging data from December 2015 were used to develop an updated surficial (alluvium, saprolite, and transition zone) and bedrock water-level maps provided in Part 2 of the CAP (Figure 2-1 and Figure 2-2, respectively, Appendix C). The surficial potentiometric data was combined with the transition zone data because the aquifers do not appear to be isolated. Groundwater flow remains consistently to the west and southwest toward the French Broad River. During the April to July 2015 data collection period, the groundwater hydraulic gradient calculated from the northeast edge of the 1982 Ash Basin to the dam wall along the southwest edge of the basin averaged 0.03 foot/foot. During this same four-month period, the hydraulic gradient calculated from the dam wall along the southwest edge of the 1982 Ash Basin to the wells along the French Broad River averaged 0.06 foot/foot. For the June 2015 contour figures, water levels in a combined 107 wells and piezometers were gauged within a 24-hour period on June 29, 2015. This provided a snapshot in time of the groundwater elevation data for the multiple flow systems observed at the Site (Table 6-2, Appendix B). The potentiometric surfaces developed from the June 2015 water level measurements for the combined surficial/transition zone and bedrock hydrogeologic zones indicate a substantial variability in the Site horizontal gradients (Table 6-2, Figures 6-10 and 6-11, and Appendix B). The horizontal gradients were used with Site-specific slug test hydraulic conductivity values and average porosities to calculate groundwater flow velocities at the Site (Appendix G of CSA report). The resulting groundwater flow velocities range from 0.61 foot to 3,266 feet per year. The highest values are observed near the ash basins due to the increased hydraulic gradients that are related to the location of the basins at topographic highs. Vertical groundwater gradients were also calculated using select well pairs (Table 6-4, Appendix B). The wells in upland areas indicate downward vertical gradients of 0.9 foot, and the remaining well clusters show vertical gradients near equilibrium (Section 6, CSA report [SynTerra 2015a]). The CSA Supplement 1 presents the following additional information. A comprehensive, site- wide round of water level measurements from all site monitoring wells was collected during a 24-hour period on December 17, 2015 for comparison to previous measurements collected during June 2015 for the CSA. The water level data are presented in Table 1-6 (Appendix B). No significant changes in water levels or groundwater flow directions were noted in December 2015 as compared to the June 2015 water level map included in the CSA Report (SynTerra, 2015a). However, it was also noted that the recent ash excavation and dewatering of the 1982 Ash Basin has effectively lowered the potentiometric surface in adjacent downgradient compliance wells (CB-2, CB-3R) that have had significant decreases in water elevation since the basin dewatering began in 2012. Hydrograph data is shown on Figure 1-80 (Appendix B), and is summarized in the CSA Supplement 1. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 39 4.8 Figures: Cross Sections Vertical and Horizontal Extent of CCR within the Impoundments As previously discussed, groundwater at the site generally flows from east to west, from the ash basins toward the French Broad River, following topography. Similarly, the COIs are expected to be highest near the ash basins with transport toward the west. The area of groundwater concentrations exceeding 2L are identified under the ash basins and to the west along groundwater flow lines up to the French Broad River (Figure ES-1, Appendix B). The vertical and horizontal extent of ash at the Site is illustrated in relation to local hydrogeologic zones underlying and surrounding the ash basins, including the vertical extent of areas where groundwater quality standards exceed the 2L or IMAC standards in plan layout view and in cross-sections developed form the drilling and monitoring program (CSA report [SynTerra 2015a]). Relevant available figures from the CSA report (Appendix B) are listed below.  Plan Layout Figures (Appendix B): o General Site map with cross-section lines, well locations, and boundaries, Figure 2-1; o Geologic map with ash basin delineations, Figure 6-1; o Surficial soil exceedances of COIs, Figure 8-3; o Groundwater 2L exceedances for ash pore water, surficial, transition zone, and bedrock wells, Figures 10-1 to 10-4; o Ash pore water well isoconcentration maps of antimony, arsenic, boron, chloride, chromium, cobalt, iron, manganese, pH, sulfate, thallium, TDS, and vanadium, Figures 10-5 to 10-17; o Surficial groundwater well isoconcentration maps of antimony, arsenic, boron, chloride, chromium, cobalt, iron, manganese, pH, sulfate, thallium, TDS, and vanadium, Figures 10-18 to 10-30; o Transition zone groundwater well isoconcentration maps of antimony, arsenic, boron, chloride, chromium, cobalt, iron, manganese, pH, sulfate, thallium, TDS, and vanadium, Figures 10-31 to 10-43; o Bedrock groundwater well isoconcentration maps of antimony, arsenic, boron, chloride, chromium, cobalt, iron, manganese, pH, sulfate, thallium, TDS, and vanadium, Figures 10-44 to 10-56; o Detection monitoring results for ash, surficial, transition zone, and bedrock wells, Figures 10-57 to 10-60; o Assessment monitoring results for ash, surficial, transition zone, and bedrock wells, Figures 10-61 to 10-64. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 40  Cross-section Figures (Section line locations depicted in Figure 2-1, Appendix B): o Geology and water level, Figures 6-3 and 6-4; o Geology and water level with photographs of core, Figures 6-5 to 6-9; o Conceptual Site model with area of COIs greater than 2L and IMAC, Figure 6- 12; o Geology and water level with groundwater and soil analytical results for sampled monitoring wells and borings, Figures 8-1 and 8-2; o Geology and water level with individual COIs (antimony, arsenic, boron, chromium, chloride, cobalt, iron, manganese, sulfate, TDS, thallium, vanadium, Figures 11-1 to 11-12. The CSA Supplement 1 contains updated geologic cross sections for various COI’s. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 41 5. GROUNDWATER MODELING ANALYSIS As previously discussed in Section 2.2, NCDEQ granted permission for Duke to submit the CAP in two phases. Part 1 of the CAP was submitted on November 20, 2015. Part 1 includes background information, a brief summary of the CSA findings, a brief description of site geology and hydrogeology, a summary of the previously completed receptor survey, a description of 2L and 2B exceedances, proposed site-specific groundwater background concentrations, a detailed description of the site conceptual model, geochemical assessment and modeling, and numerical groundwater flow and transport modeling used to evaluate the effects of various potential closure options on groundwater and surface water quality. The second part of the CAP was submitted on February 19, 2016, and identifies updated numerical modeling results, alternative corrective actions, the proposed corrective action, conceptual plans for recommended corrective actions, implementation schedule, and a plan for future monitoring and reporting. The groundwater modeling analysis prepared by SynTerra is presented as a combination of assessments including the following:  SCM development;  Geochemical assessment and modeling;  Numerical flow and transport modeling. The information from each of the above assessments was successively used to develop the next in order to develop a complete model of the system. Modeling in Part 1 of the CAP was used to assess source handling and control options with the following scenarios:  Existing Conditions;  Capping Ash Basins;  Removal of Ash. Ash removal by excavation with lowering of the dams, and installation of drains was proposed as the recommended source control option and modeling in Part 2 of the CAP addresses alternative remedial alternatives to restore groundwater after ash removal including:  Monitored Natural Attenuation;  Groundwater Extraction;  In-Situ Chemical Immobilization;  Permeable Reactive Barrier. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 42 The modeling results were then used to select the final combined recommended remedial approach following specific alternative evaluation criteria described in detail in Section 6.0 of the CAP Part 2:  Effectiveness;  Implementability/Feasibility;  Environmental Sustainability;  Cost; and  Community Acceptance. Modeling applied with the above alternative evaluation criteria, resulted in selection of monitored natural attenuation as the proposed groundwater restoration alternative. After initial selection of Monitored Natural Attenuation, the modeling results were used to assess the effectiveness against the EPA guidance methods for monitored natural attenuation using a tiered approach. The four tiered objectives from EPA cited by SynTerra are: I. Demonstration that the ground-water plume is not expanding and that sorption of the contaminant onto aquifer solids is occurring where immobilization is the predominant attenuation process; II. Determination of the mechanism and rate of the attenuation process; III. Determination of the capacity of the aquifer to attenuate the mass of the contaminant within the plume and the stability of the immobilized contaminant to resist re-mobilization, and; IV. Design performance monitoring program based on the mechanistic understanding developed for the attenuation process, and establish a contingency plan tailored to the site-specific characteristics. The final result of the modeling efforts by SynTerra is the recommendation for ash removal, dam lowering, and installation of drains, followed by monitored natural attenuation. The following section presents the SCM. Predictions for post-closure groundwater elevations are included in the figure, “Predicted Post-Closure Groundwater Elevation, Asheville Steam Electric Plant, Arden, North Carolina,” included in Appendix B. Each assessment detailed in Part 1 and 2 of the CAP is summarized in the following sections. 5.1 Site Conceptual Model SynTerra developed and summarized the components of a SCM for the Asheville Plant area in Section 11 of the CSA report, and Section 3 of the CAP Part 1 (SynTerra 2015b), and used it as the basis for the development of the numerical groundwater transport model presented in Part 1 of the CAP. The SCM was developed from data (discussed in Section 4) generated during previous assessments and existing groundwater monitoring data. The SCM was modified based Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 43 on the results of the 2015 groundwater assessment activities and included geochemical testing and analysis described in Part 1 of the CAP and further refined in Part 2 of the CAP. The SCM identifies the following key aspects for model development and predictions of potential impacts:  The two ash basins, designated as the 1964 and 1982 ash basins, and a constructed wetlands used for FGD treatment within a portion of the 1964 ash basin, are identified as the source of potential COIs;  Groundwater wells immediately downgradient of the constructed wetlands indicate potential impact from FGD blowdown wastewater;  The subsurface geology at the Asheville Plant is composed of alluvium in the French Broad River valley, saprolite, a transition zone, and fractured shallow bedrock;  Groundwater flow is unconfined and generally follows topography;  Groundwater flow is from the east and dominated by Lake Julian at higher elevation (2160.7 feet mean sea level [MSL]), and discharges to the French Broad River in the west at lower elevation (2030 feet MSL), that then flows north;  The primary factor in constituent transport across the site is hydraulic control, with the hydraulic head at Lake Julian and significant topographic relief driving groundwater flow through the system from the ash basin to the French Broad River;  Groundwater flow from the Lake Julian area to the French Broad River occurs over less than half a mile;  Groundwater is significantly influenced by the unlined, secondary settling basin at the northeastern corner of the 1964 ash basin with an average water level of 2137 f eet MSL;  Groundwater is recharged by Lake Julian and aerial precipitation that also occurs within the ash basins;  Coal ash is primarily above the existing water table, but historically would have been below the water table during sluicing operations;  The ash basin source areas discharge pore water to the subsurface beneath the basins and via seeps through the embankments;  Forty-one private water wells have been identified within one-half mile of the site, with more than half on the west side of the French Broad River, and a large number south of the site;  The primary site-specific COIs identified as being above 2L or IMAC standards in ash pore water are: antimony, arsenic, boron, chromium, cobalt, iron, manganese, sulfate, thallium, TDS, vanadium, and pH; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 44  Boron and cobalt are the most prevalent COIs in downgradient groundwater. The identified boron plume extends to saprolite, the transition zone and bedrock groundwater, and to wells west of the French Broad River;  Boron concentrations are elevated in a localized area downgradient from the northwest corner of the constructed wetlands, but are typically significantly below 2L standards and generally less than the detection limit in background wells;  Cobalt is identified in groundwater throughout the site at concentrations above the IMAC without a distinct plume, having similar values identified in background wells and ash pore water, and transition concentrations that often exceed ash pore water values;  Boron, chloride, cobalt, sulfate, and TDS were selected as a subset of site-specific COIs to represent the extent of contamination for further modeling because values of other COIs either do not significantly exceed background levels, and/or no discernable existing associated plume is downgradient from the ash basins. 5.2 Geochemical Modeling The geochemical modeling detailed in Part 1 of the CAP (SynTerra 2015b) provides qualitative and quantitative estimations of key COIs behavior in the Site environment. The geochemical modeling and assessment results were performed to address site-specific processes and characteristics identified in the SCM. Part 1 of the CAP presents a detailed discussion of the geochemical properties of the COIs in relation to site-specific materials and how these properties relate to the retention and mobility of these constituents. The mobility of the COIs is addressed in a detailed soil sorption evaluation provided in Part 1 of the CAP, (Appendix B) that had the objective of providing site-specific sorption coefficients (Kd) for each COI for use in numerical modeling and incorporates effects related to oxidation/reduction potential (EH) and pH. In Part 2 of the CAP, geochemical modeling was used to assess alternative groundwater restoration scenarios and to assess site specific monitored natural attenuation against the EPA tiered approach for monitored natural attenuation. 5.2.1 Soil Sorption Evaluation SynTerra contracted the University of North Carolina at Charlotte (UNCC) to perform and analyze soil sorption characteristics. UNCC developed Kd values for COIs using 12 soil samples collected during the geotechnical and environmental exploration program at the site between March 13 and January 2, 2015 (Table 1 of Appendix C). The 12 soil samples were selected to represent the saturated zone beneath and downgradient of the ash basin. The solutions used in both the batch and column sorption testing were generated in the laboratory as synthetic groundwater with targeted COI concentrations (Table 2 of Appendix C). The leachates of the batch and column testing were analyzed for 13 analytes (arsenic, beryllium, boron, cadmium, chromium, cobalt, antimony, iron, manganese, nickel, selenium, thallium, and vanadium). Desorption assessment was subsequently performed on column tests by application of six pore volumes of laboratory-grade water to assess the potential for COI mobilization after sorption. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 45 Leaching analysis of two ash samples from each basin, 1982 and 1964, was also conducted using standard Methods 1313 and 1316 to assess the source of COIs. The soil sorption evaluation by UNCC assumed that metal oxy-hydroxide phases of iron, manganese, and aluminum in the soil samples are the most important phases in terms of sorption of COIs, and provided quantitative analysis of these phases in the soil samples. UNCC identified general concerns with applying batch and column testing results to the field results, and key findings of the soil sorption evaluation. Soil Sorption Evaluation General Comments:  The synthetic groundwater used differs from in-situ groundwater chemistry, and the soil samples were originally exposed to different geochemical conditions before testing;  The geochemical interaction of COIs with the soils in the same testing solution may result in different sorption characteristics;  Tests were performed at atmospheric conditions, and redox conditions were not adjusted to represent field conditions. The sorption results are reflective of the redox conditions in the lab and may not be representative of other redox conditions;  The soil samples were sieved to less than 0.30 millimeter before testing, which could affect the laboratory-determined Kd value. Soil Sorption Evaluation Key Findings:  The batch and column testing for most COIs yielded results that were typically within one order of magnitude difference for each COI, with the exception of cadmium, chromium, cobalt, nickel and vanadium, which spanned two orders of magnitude;  The batch test for boron was inconclusive. A Kd value could not be determined due to non-linear behavior, negligible sorption, and/or leaching of boron from the soil sample. The column experiment for boron produced a Kd range from less than 10 to 75 milliliters per gram (mL/g);  Iron and manganese were not included in the synthetic groundwater solution, but their presence in leachates provide insight into their potential for leaching;  Ash leaching tests indicated negligible (close to the detection limit of 1 part per billion) leaching of beryllium, cadmium, cobalt, copper, nickel, lead, thallium and zinc;  Ash leaching tests indicated increased concentrations of arsenic, boron, chromium, iron, molybdenum, selenium, and vanadium in the leachate solution, and the leachate concentrations of these COIs were higher for the 1982 basin test compared to the 1964 basin test. An addendum to the initial UNCC soil sorption evaluation study was provided in Part 2 of the CAP to include calculation of three sorption isotherm equations for the batch testing data provided in Part 1 of the CAP. Isotherm equations are presented in Appendix D of Part 2 of the Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 46 CAP. Linear, linear with irreversible sorption fraction, and Freundlich sorption isotherms equations for antimony, arsenic, beryllium, boron, cadmium, chromium, cobalt, nickel, selenium, thallium, and vanadium are included in tabular and graphical format. 5.2.2 Geochemical Numerical Modeling Analysis In addition to the geochemical sorption testing and analysis performed by UNCC, SynTerra contracted Brian Powell, Ph.D., to perform a geochemical assessment and modeling of the overall mobility of COIs at the site. The results of this testing and analysis are presented in detail in Appendix C of Part 1 of the CAP and updated with modeling results using additional site specific data in Appendix C of Part 2 of the CAP. The geochemical assessment and modeling includes the sorption processes performed by UNCC and precipitation/coprecipitation reactions involving COIs and mineral phases. This assessment also accounted for geochemical reactions and COI speciation influenced by the pH and EH of the pore water at the site. The geochemical modeling was performed using the USGS program PHREEQC and the results were compared to the UNCC Soil sorption evaluation study results (Table 5.1 of Appendix C). In Part 1 of the CAP sorption was modeled as being associated only with hydrous ferric oxide (HFO) using values based on the measured extractable iron content of the aquifer solids in site samples. In Part 2 of the CAP additional data, including extractable iron and aluminum concentrations, was used in the numerical modeling of COIs to account for HFO, gibbsite (HAO), and potential variations in site specific pH and EH, using averages, minimums and maximums to bracket values, that could occur due to system changes associated with remediation. The CAP Part 2 assessment compares Kd values obtained from PHREEQC simulations of sorption with sorption identified in Part 1 of the CAP from UNCC laboratory batch testing. In summary, the geochemical modeling identified the following results:  Boron as borate, barium, and zinc were identified as being relatively mobile with low Kd values;  Boron has the lowest experimentally and simulated Kd, and therefore is assumed to be a conservative representation of known areas of groundwater impact;  Arsenic, iron, manganese, selenium, and vanadium also were identified as having low Kd values, but were predicted for the “worst case” scenario. The modeled EH and pH conditions similar to those during the UNCC laboratory testing produced generally similar results as the UNCC tests for these COIs;  The modeled and the experimental boron sorption were significantly different (1000x), where boron sorption was underpredicted by the modeling. In either case, boron is considered highly mobile under site conditions;  Sorption processes were identified as a dominant removal mechanism, and the number of sorption sites required for complete removal of the total of all constituents in solution is calculated as less than 1% of the available sorption sites. It is concluded that sufficient Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 47 sorption capacity exists for removal of high concentrations of all COIs (Table 6.2 Appendix C). Recommendations and limitations of the geochemical modeling from Part 1 of the CAP include:  Consideration of aluminum oxide surface for sorption should be included to improve predictions, and may in part be related to the observed differences between experimental and modeled Kd values for boron;  Additional studies to identify sorption site density of solid phases for soils are needed to verify assumptions on site densities used in modeling;  Additional speciation data is needed to verify predicted oxidation states of arsenic, selenium, vanadium, and other redox-sensitive COIs under site conditions;  Predictive geochemical modeling using fixed EH and pH site-specific conditions could be used to verify observed field data for model verification;  A statistical analysis of the correlation between dissolved COIs and dissolved organic carbon in pore waters is recommended to identify potentially associated sorption relationship to COI mobility. Part 2 of the CAP addressed some of the above recommendations and limitations including:  Assessment of aluminum oxide surface sorption;  Incorporation of additional data to support sorption site density;  Incorporation of pH and EH data to support predicted oxidation states for redox-sensitive COIs under site conditions. 5.3 Numerical Groundwater and Transport Modeling SynTerra provided a detailed numerical groundwater flow and transport model report in Appendix D of Part 1 of the CAP (SynTerra 2015b) and updated modeling results in Part 2 of the CAP (SynTerra 2016a). The model was based on the SCM and geochemical modeling and assessment using MODFLOW to simulate hydrologic flow, and MT3DMS to simulate COI transport. The numerical flow and transport models were developed such that the key site- specific geological and hydrogeological features identified in the SCM and geochemical assessment influencing the migration, chemical, and physical characteristics of contaminants are represented. The described numerical groundwater model is a three-dimensional groundwater flow and contaminant fate and transport model having the objective of predicting the following in support of the CAP:  Predict concentrations of the COIs at the compliance boundary or other locations of interest over time;  Estimate the groundwater flow and constituent loading to surface water discharge areas; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 48  Predict approximate groundwater elevations in the ash for the proposed corrective action;  Predict fate and transport of COIs for the different remedial alternatives for groundwater restoration. The model and model report were developed in general accordance with the guidelines found in the memorandum Groundwater Modeling Policy, issued by NCDEQ DWQ on May 31, 2007 (DEQ modeling guidelines). 5.3.1 Numerical Groundwater Flow Model Description The MODFLOW model includes the following features:  The model covers an area of approximately 802.5 acres centered on the site, and includes Lake Julian and the French Broad River as constant-head boundary conditions to the east and west, respectively;  Surface topography was interpolated from NCDOT LIDAR data;  Ash basin top elevations, for both the 1964 and 1982 ash basins, came from site-specific survey data;  Geologic grids developed from interpolation between well boring logs and represented by 16 model layers were discretized horizontally at a 40-foot by 40-foot spacing, resulting in 240,202 active cells;  Hydraulic conductivities were determined through calibration;  Recharge was set as 6 inches per year for upland areas, and 1 inch per year historically at the Plant site for the dams of Lake Julian and the two ash basins to represent the impervious nature of the facility and compacted soils. The ash basins during current conditions had infiltration rates of 6 and 12 inches per year for the 1982 and 1964 basins, respectively. Final basin recharge rates ranged from 12 to 24 inches per year;  The settling pond in the 1964 basin and dewatering basin in the 1982 basin were also set as constant-head boundaries within the model;  Creeks and drains determined from LIDAR elevations were assigned in the model using the MODFLOW DRAIN feature;  Steady-state flow calibration targets included 97 water level measurements taken in June 2015. Sensitivity analysis of the flow model was performed after calibration. The results indicated that the numeric flow model is insensitive to small changes in the main hydraulic conductivity parameters, the model is more sensitive to changes in the bedrock hydraulic conductivity value compared to shallow layers, and the uncertainty is likely a factor of 2 or more, but less than an order of magnitude. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 49 5.3.2 Numerical Groundwater Transport Model Description Transport was assessed using MT3DMS with the MODFLOW-generated transient flow velocity fields representing the time from January 1964 to July 2015. The transient flow field began with steady-state conditions, followed by development history of the 1964 and 1982 ash basins broken into three successive periods: 1. High infiltration rate in the 1964 basin representing ash sluicing from 1964 to 1982; 2. Increased infiltration rate in the 1982 basin from 1982 to 2013; 3. Current basin infiltration rates from 2013 to 2015. The combined CAP Part 1 and 2 transport modeling took into account the following characteristics:  Boron, chloride, cobalt, manganese, sulfate, and TDS selected as a subset of site- specific COIs to represent the extent of contamination for modeling;  Source concentrations in the ash basins identified in ash pore water samples;  Soil-water distribution coefficients (Kd) for the lowest UNCC cobalt value (2.5 mL/g), and a default low value of 0.1 mL/g to represent boron and sulfate retardation consistent with other sites;  Longitudinal, transverse and vertical dispersivity of 20 f eet, 2 feet, and 0.2 feet, respectively;  Effective porosity of 0.2 in unconsolidated layers and 0.001 in bedrock layers;  Soil dry bulk density of 1.6 g/mL. Initial background COI concentrations were set as zero concentration to represent no impacts in 1964. The saturated cells within layers 3–7 underlying the ash basins were assigned constant concentrations to represent the source of COIs. The report notes that the placement of constant concentrations several feet deeper than the ash basins potentially results in an overestimate of the COIs in groundwater below the basins. The transport of COIs was then calibrated to concentrations measured in samples from 98 monitoring wells in June 2015. The calibrated model comparison of simulated to measured boron, chloride, cobalt, sulfate, and TDS concentrations is listed in Tables 6, 7, 8, 9, and 10 of Appendix C, respectively. 5.4 Groundwater Chemistry Effects Predictions of groundwater chemistry effects were modeled for three possible source control scenarios presented in Part 1 of the CAP: 1. Closure Model Scenario #1 (CMS1) – no further action; Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 50 2. Closure Model Scenario #2 (CMS2) – complete ash removal from the 1982 and 1964 Ash Basins, installation of drains along the bottom of the former ash basins, and backfilling and regrading of the former ash basins with clean fill to 2110 feet and 2120 feet MSL based on the Amec Foster Wheeler Environment & Infrastructure (Amec Foster Wheeler) ash basin closure design (2015) (Figure 29 of Appendix C); 3. Closure Model Scenario #3 (CMS3) – adds an impermeable surface cap to CMS1. All source control scenario predictions were used to provide simulated results through year 2045, and results in Appendix D of the CAP Part 1 are presented at 5 years (2020), 15 years (2030), and 30 years (2045). Results provided in the CAP Part 1 are only presented for boron under the assumption that it provides the most conservative estimate of widespread transport. Boron is considered the most conservative COI based on laboratory sorption evaluation and geochemical modeling. However, updated modeling results are provided in the CAP Part 2 to address potential source contribution of manganese, sulfate and TDS concentrations by applying observed concentrations to model simulations for these constituents. A manganese concentrations of 7000 µg/L in the western parts of the 1964 and 1982 basins, and a manganese concentration of 1000 µg/L for the eastern parts of the basins. The model report results for the CMS1 scenario indicate that the boron plume is stabilized after 30 years, and little change occurs. This is because the boron plume has already reached the French Broad River from the 1964 ash basin, while the boron plume from the 1984 basin recedes due to reduced infiltration through the ash basin. The model results for the CMS2 scenario indicate little effect on the boron plume within the first 2 years, but by 2030 the simulation predicts that the boron plume in the shallower part of the system will be significantly reduced (Figure 39 of Appendix C), as will the southern area of the deeper part of the system (Figure 40 of Appendix C). By year 2045, the simulation predicts that the extent of boron will be greatly reduced, both horizontally and vertically (Figures 41 and 42 of Appendix C). The dominant concentration reduction mechanism is dilution by flushing of groundwater from upgradient toward the French Broad River. The remaining boron is identified in lower conductivity zones which receive less flushing. The model results for CMS3 are relatively similar to those identified for CMS1 with the exception that the boron plume is slightly reduced for CMS3 compared to CMS1. While predictions are based on the conservative nature of boron, Part 1 of the CAP identified that the pH and oxidation/reduction potential has a fundamental influence on the extent of contaminant mobility for redox sensitive COIs. Part 2 of the CAP addressed alternative corrective action measures for groundwater restoration which required additional numerical transport modeling of fate and transport of COPCs to evaluate the effectiveness of the different remedial alternatives. The alternative corrective action measures evaluated are:  Monitored Natural Attenuation (MNA); Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 51  Groundwater Extraction (recovery wells or trenches) with fracture enhancement option;  In-Situ Chemical Immobilization;  Permeable Reactive Barrier. Each alternative was evaluated and discussed in Section 6.0 of Part 2 of the CAP including model simulations to support the final recommended approach. The groundwater extraction simulation included a line of 10 bedrock pumping wells covering 800 feet located beyond the northwest corner of the 1964 ash basin along the access road near the toe of the 1964 dam, and eighty feet into the saturated bedrock. The simulation indicated that each of the 10 wells was able to sustain a pumping rate of 0.3 gpm for a combined total of 3 gpm resulting in drawdown of 10 to 20 feet in each well. The boron transport simulation with source excavation. MNA, and groundwater extraction indicates that the bulk of the boron plume mass is removed by the year 2030 with some smaller areas of boron mass remaining through 2045. A comparison of simulated boron concentrations over time resulting from source excavation with monitored natural attenuation (MNA), and with groundwater extraction is provided in Figure 3-1 in Part 2 of the CAP. Section 7.0 of Part 2 of the CAP provides the final proposed corrective actions based on data and numerical modeling assessment from both Parts 1 and 2 of the CAP, with subsequent evaluation of each piece to assure compliance in a timely manner, and includes the following:  Source Control – ash basin closure and source removal. Soils left on site after ash removal will be sampled and analyzed, and results will be incorporated into fate and transport modeling to assess the potential for modification to the corrective actions;  Elimination of Potential Receptors – installation of the Bear Leah Trail public water supply line has resulted in replacing five private water wells that are planned for subsequent geophysical survey and abandonment;  Monitored Natural Attenuation – SynTerra identified that the groundwater impacted by the ash basin does not pose unacceptable risks to either human health or ecological receptors further discussed in Section 5 of Part 2 of the CAP. And as supported by groundwater flow and geochemical modeling, attenuation of COPCs will be achieved by a combination of dilution, dispersion, and limited sorption. Simulated manganese concentrations, and updated simulations of sulfate and TDS are provided in Appendix B of Part 2 of the CAP. The results of modeling the monitored natural attenuation alternative are presented in Figure 3- 1 of Part 2 of the CAP for predictions at years 2020, 2030, and 2045. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 52 5.5 Groundwater Trend Analysis Methods The CSA Report indicates that historical analytical results from compliance and voluntary groundwater monitoring wells were used to assess background groundwater quality and assess results against existing IMAC and 2L values. Compliance groundwater monitoring wells were sampled as part of the CSA Report to supplement the expanded groundwater assessment. Time series plots of existing data comparing compliance, background wells, and 2L standards, where applicable, were shown on Figures H1 through H21 of Appendix B. Groundwater monitoring data collected from the four compliance monitoring wells were evaluated by SynTerra using interwell prediction limits (parametric, nonparametric, and Poisson) to compare background well data (CB-01 and CB-09) to the results for the most recently available sample data from compliance wells collected in April 2015. The detailed description is in Section 10.0 of the CSA (SynTerra 2015a). Before statistical assessment, the dataset was assessed and treated using guidance from ASTM D6312-98 and USEPA 2007. COIs with exceedances of the 2L or IMAC are identified in all compliance boundary wells at statistically elevated values over concentrations observed in designated background wells CB-01 and CB-09 (Table 2-2, Appendix B). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 53 6. BENEFICIAL REUSE AND FUTURE USE 6.1 CCR Material Reuse From 2007 through summer 2015, a portion of the CCR materials from the 1982 Ash Basin was excavated and transported to the Asheville Regional Airport for beneficial use. The airport extended its runway/taxiway network by using the CCR as permitted structural fill in compliance with existing permits. Ash transport to the Asheville Regional Airport ended in summer 2015. Duke considers CCR beneficial use in an environmentally responsible manner for ash that is produced at its plants or is removed from existing ash basins. Ash basin closure by removal presents the opportunity for CCR beneficial use. Duke has a team dedicated to identifying beneficial use opportunities and evaluating their feasibility. Consistent with North Carolina CAMA requirements, Part III, Section 4(e), Duke issued a request for proposals to conduct a beneficial use market analysis, study the feasibility and advisability of installing existing beneficiation technologies, and examine innovative technologies. At this time, no CCR beneficial use opportunities have been identified for the remaining CCR materials. Findings indicate that large-scale beneficiation technologies are not feasible to install at this time. 6.2 Site Future Use The anticipated future use of the 1964 Ash Basin is undetermined at this time. Possibilities for this Ash Basin include but are not limited to a permitted structural fill, a solar farm, or simply being reseeded with grass. The closure design of the 1964 Ash Basin is planned to include a balanced breach, in which the impoundment will be excavated to a design elevation. The basin will be backfilled to promote drainage, resulting in a non-impounding structure. The backfill will also be graded in a way to allow stormwater flows from the basin to pass through an existing culvert under I-26. In contrast to the 1964 Ash Basin, the closure plans for the 1982 Ash Basin were developed to facilitate the construction of the proposed Combined Cycle Plant. This Plant will be located within the footprint of the 1982 Ash Basin. The closure design of the 1982 Ash Basin includes a dam breach to an elevation of 2106 feet, with an engineered fill to this same minimum elevation within the existing Ash Basin. After completion of the balanced breach, additional fill will be placed to facilitate construction of the Combined Cycle Plant to design grades. After the completion of the Combined Cycle Plant, the existing coal-fired generating plant will be decommissioned. Duke intends to cease operation of the coal-fired units in accordance with CAMA, but specific details of future decommissioning and demolition have not been developed at this time. The property deed will be recorded to document the site conditions at the time of closure. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 54 7. CLOSURE DESIGN DOCUMENTS 7.1 Engineering Evaluations and Analyses As part of the closure design process, engineering evaluations and analyses (calculations) were developed for the 1982 Ash Basin and are included in Appendix D. Engineering evaluations and analyses will be developed in the future for the 1964 Ash Basin. The basins are required to be closed by 2022, and each basin must be closed such that it will not impound water. Ash has been removed from the 1982 Ash Basin, and dam decommissioning is currently underway. Excavation of the 1982 Ash Basin was completed on September 30, 2016. The ash basin was then turned over for dam decommissioning and construction of the natural gas combined cycle plant. The proposed decommissioning of this ash basin dam is shown on the drawings referenced in Section 7.2. Additional fill will be placed to support a combined cycle plant. To construct the fill, the existing embankment will be breached to create a non-impounding structure, and this material will be placed in the existing ash basin. Borrow material will also be obtained from onsite borrow areas to support the combined cycle plant construction. This borrow material will be placed and compacted in accordance with the CQA Plan referenced in Section 7.3. Drainage ditches are also incorporated into the final configuration to route the 100 year – 24 hour flow to an existing culvert under I-26. 7.2 Site Analysis and Removal Plan Drawings The design drawings associated with the dam decommissioning of the 1982 Ash Basin are included in Appendix E. These drawings were developed for three separate submittals and resulting approvals from NCDEQ: 1) Decommissioning and Ash Removal Closure Plan drawings, 2) Erosion and Sediment Control Plan drawings, and 3) Stormwater Management Plan drawings. Design drawings for the dam decommissioning of the 1964 Ash Basin will be prepared and submitted to NCDEQ at a later date. 7.3 Construction Quality Assurance Plan The purpose of the CQA Plan is to identify the quality assurance procedures, standards, and methods that will be employed during the project to provide assurance that the requirements of the drawings, specifications, and regulatory permits are met. The CQA Plan is specific to the Asheville 1982 and 1964 Ash Basins Closure Design, and is prepared in compliance with CAMA. The CQA Plan is included and attached to this document in Appendix F. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 55 8. MANAGEMENT OF WASTEWATER AND STORMWATER 8.1 Stormwater Management Ash removal within the 1982 Ash Basin is complete, and dam decommissioning activities are currently underway to prepare the site for construction of a natural gas combined cycle plant. At the conclusion of dam decommissioning activities, stormwater flows will exit the basin through permitted stormwater channels along the toe of the dam breach. Stormwater management for the 1982 Ash Basin is detailed on the drawings in Appendix E. Stormwater from the 1964 Ash Basin currently drains to the Duck Pond within the ash basin. The goal of the 1964 Ash Basin decommissioning is to return the former ash basin to a natural state where stormwater is discharged via sheet flow to the receiving water(s), such as the French Broad River, and eliminate the requirement for an NPDES stormwater permit. To accomplish this, multiple phases of decommissioning work are required. The following section provides additional details for the current wastewater and stormwater management operations within the 1964 Ash Basin. 8.2 Wastewater Management The Rim Ditch system receives the sluiced ash and water from the Plant. Water from the Rim Ditch is pumped through a center pond filter system to the stilling basin located to the north of the 1964 Ash Basin, and then out through NPDES Outfall 001. The wastewater treatment system will continue to be operated in this manner until such time that the coal fired plant is retired, and ash and effluent discharges from the plant to the 1964 Ash Basin cease. Subsequent to plant and Rim Ditch retirement, additional water management and treatment systems will be required in accordance with the DEQ letter from Jeff Poupart, Water Quality Permitting Section Chief, to Duke Energy on July 20, 2016 regarding decanting of coal ash impoundments. Management of wastewater will also be addressed as the coal operations become inactive. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 56 9. DESCRIPTION OF FINAL DISPOSITION OF CCR MATERIALS From early 2007 through summer 2015, the CCR materials from the 1982 Ash Basin were excavated and transported by truck to the Asheville Regional Airport and beneficially reused as structural fill. The airport used the ash for projects aimed at extending the runway/taxiway network. The off-site removal details for the Asheville Regional Airport are presented below:  Facility location and name: Asheville Regional Airport, 61 Terminal Drive, Fletcher, NC 28732;  Facility permit number: Structural Fill Permit # WQ0000020;  Facility type: Permitted structural fill for runway/taxiway construction. Beginning in fall 2015, Duke started transporting the remaining CCR in the 1982 Ash Basin to an off-site fully lined landfill near Homer, Georgia. From February 2016 through October 2016, ash was transported to an additional landfill located in Mooresboro, North Carolina. Currently, ash from the 1964 Ash Basin is being transported to the landfill near Homer, Georgia. The off- site removal details for the Georgia landfill are presented below:  Facility location and name: R&B Landfill, 610 Bennett Road, Homer, GA 30547;  Facility permit number: Permit 006-009D(MSWL);  Facility type: Solid Waste Handling - Permitted landfill. The off-site removal details for the North Carolina landfill are presented below:  Facility location and name: Duke Energy Rogers CCP Landfill, 573 Duke Power Rd, Mooresboro, NC 28114;  Facility permit number: Solid Waste Management Facility Permit No. 8106;  Facility type: Solid Waste Management Facility. Duke continues to consider future disposal and/or beneficial reuse opportunities. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 57 10. APPLICABLE PERMITS FOR CLOSURE Implementation of the Ash Basin closure at the Asheville Steam Electric Generating Plant will require permits issued by regulatory authorities. A list of the anticipated permits required for closure is below:  Dam Breach Certificate of Approval to Repair/Modify for Decommissioning Dam Structures;  Discharge Permits for Wastewater and Stormwater;  Solid Waste Permits for Landfills and Structural Fills (by others); and  Erosion and Sedimentation Control Permits. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 58 11. POST CLOSURE MONITORING AND CARE The Post-Closure Operations Maintenance and Monitoring (OM&M) Plan is provided as Appendix G. The default post-closure period is 30 years; however, opportunities to modify and reduce the post-closure period for various requirements including groundwater and surface water monitoring are possible. The Post-Closure OM&M Plan addresses the following:  Description of the closure components;  Regular inspections and maintenance of the stormwater and erosion control measures;  Post-closure inspection checklist to guide post-closure inspections;  Continuation of the groundwater and surface water monitoring and assessment program;  Provide means and methods of managing affected groundwater and stormwater;  Maintaining the groundwater monitoring system;  Facility contact information;  Description of planned post-closure uses. 11.1 Groundwater Monitoring Program The (CSA report [SynTerra 2015a]) provides an interim groundwater monitoring plan to bridge the gap between completion of CSA Report activities and implementation of the pending Groundwater Monitoring Plan and CAP. The interim groundwater monitoring plan provided in the CSA is also summarized in Section 3.3.2 of this document. The proposed constituents, parameters, and sampling locations for the interim groundwater monitoring plan were presented in Section 16.0 of the CSA report (SynTerra 2015a) and is updated in Part 2 of the CAP in relation to proposed remedial actions. With the submittal of part 2 of the CAP SynTerra has provided a proposed updated Interim Monitoring Plan (IMP), and a post-closure Effectiveness Monitoring Program (EMP) as required by CAMA in Section 9.0 of Part 2 of the CAP. The EMP is to begin after implementation of the basin closure groundwater Corrective Action Plan, with the IMP being implemented within 30 days of CAP approval by CAMA. The proposed updated IMP consists of sampling groundwater and surface water for the constituents listed in Part 2 of the CAP (Table 9-1 of Appendix C) on a semi-annual basis, with the sampling frequency of background wells being modified to achieve a minimum of eight sets of data prior to implementation of the EMP. Reporting will be annually. The IMP will also be periodically evaluated and modified as needed. The proposed IMP sampling locations for groundwater are provided in Table 9-2 of Appendix C, and surface water and seep sampling locations are provided in Table 9-3 of Appendix C. Groundwater, surface water, and seep sample locations are presented spatially in Figure 9-1 of Appendix C. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 59 The proposed EMP program also consists of sampling groundwater and surface water for the constituents listed in Table 9-1 of Appendix C on a semi-annual basis, and is intended to support triannual NPDES compliance monitoring with a reduced frequency if monitoring results are consistent with modeling results provided in Section 6.0 of Part 2 of the CAP. Reporting will be annually. The EMP will also be evaluated periodically and modified as needed. The proposed EMP sampling locations for groundwater are provided in Table 9-2 of Appendix C, and surface water and seep sampling locations are provided in Table 9-3 of Appendix C. Groundwater, surface water, and seep sample locations are presented spatially in Figure 9-1 of Appendix C. Additional monitoring locations may be required once the final corrective action plan is selected and implemented. Additionally, the EMP is designed to meet the requirements of the Tier 4 monitoring and the USEPA established eight objectives for performance. However, additional analysis is required to achieve all the objectives and the EMP reports will include two phases to address these. A Sampling and Analysis Plan (SAP) will be developed and adhered to once approved and prior to implementation of both the IMP and EMP. Currently, groundwater samples are planned to be collected using low-flow sampling techniques in accordance with the NCDEQ conditionally approved June 10, 2015, low flow sampling program provided in Appendix G of Part 2 of the CAP. Implementation of the IMP or EMP is scheduled to begin in the month April or November following the CAP approval. Subsequent sampling events will then follow on subsequent April and November months. The data will be reviewed annually to confirm the corrective actions are effective at protecting human health and the environment. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 60 12. PROJECT MILESTONES AND COST ESTIMATES 12.1 Project Schedule CAMA deems the Asheville Plant a “high-priority” site, which specifically requires closure of the ash basins pursuant to Part II, Section 3(c). The CAMA closure definition of dewatering to the maximum extent practicable and removing and transferring CCR to a landfill or structural fill is demonstrated in the proposed schedule. Groundwater assessment and corrective action is ongoing, and the requirements and time for restoring groundwater quality are currently unknown. The anticipated milestones are defined and shown below. The Dam Decommissioning Plan for the1982 Ash Basin has been approved by NCDEQ, and ash removal is complete. Note that the milestones are subject to change when not required by regulations. The Anticipated Activities include the following items:  Submit updated Excavation Plan annually;  Site Analysis and Removal Plan submission and concurrence;  Water Management Plan submission and approval;  End stormwater discharge into impoundments;  Cease operation of coal-fired units at the Plant;  Completion of 1964 Ash Basin Ash Removal per NC Regulations;  1964 Ash Basin Dam Decommissioning Plan submission and approval;  1964 Ash Basin Erosion & Sediment Control Plan submission and approval;  1964 Ash Basin Stormwater Management Plan submission and approval;  Closure Certification (milestone);  Closure Permit Issued (milestone);  Impoundments closed pursuant to Part II, Sections 3(b) and 3(c) of the Act;  Basin closure (groundwater compliance met); and  Beginning of Post-Closure Care Period. 12.2 Closure and Post-Closure Cost Estimate Duke is preparing closure and post-closure care cost estimates at a level of detail and from the perspective that sufficient funding will be set aside in a financial assurance mechanism for a third-party (other than the owner) to complete the scope of work. The cost estimates will be included as Appendix H of this Removal Plan at a later date. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 61 13. REFERENCED DOCUMENTS AECOM, “Additional Seismic Stability Evaluation, Asheville Steam Station, 1964 Ash Pond Dam (Issue ASH-202),” March 31, 2016. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “2012 Five-Year Independent Consultant Inspection, Cooling Lake Dam and Ash Pond Dams, Asheville Steam Electric Plant”, February 19, 2013. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “2013 Report of Limited Field Inspection, Cooling Lake Dam and Ash Pond Dams, Duke Energy Progress – Asheville Steam Electric Plant”, August 5, 2013. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler) “2014 Annual Ash Basin Dam Inspection, Asheville Steam Electric Station,” January 14, 2015. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “2014 Report of Limited Field Inspection, Cooling Lake Dam and Ash Pond Dams, Duke Energy Progress – Asheville Steam Electric Plant”, August 28, 2014. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “Asheville Plant, BUNCO- 089-H, BUNCO-097-H Observations, 8/27/2014 through 10/2/2004, Buncombe County, North Carolina”, September 8, 2014 through October 6, 2014. AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “Final Report for Task ASH-1 Issue,” August 2014 (2014a). AMEC Environment & Infrastructure, Inc. (Amec Foster Wheeler), “Asheville Steam Plant, Final Report for Task ASH-2 Issue,” August 26, 2014 (2014b). Amec Foster Wheeler, “2015 Annual Ash Basin Dam Inspection, Asheville Plant,” May 9, 2016. Amec Foster Wheeler, “2016 Annual Ash Basin Dam Inspection, Asheville Plant,” September 12, 2016 (2016b). Amec Foster Wheeler, “Asheville Plant Operations & Maintenance Manual, Rev. 3,” March 31, 2015 (2015d). Amec Foster Wheeler, “CCR Unit History of Construction, Asheville Steam Electric Generating Plant,” October 12, 2016 (2016a). Amec Foster Wheeler, “Letter Report – Waste Strategy Analysis (Revised), Asheville Steam Station,” January 14, 2015 (2015c). Amec Foster Wheeler, “Phase 2 Reconstitution of Ash Pond Designs, Final Report Submittal, Revision B, Asheville Steam Station,” July 17, 2015 (2015e). Amec Foster Wheeler, “Subsurface Exploration and Laboratory Testing Data Report, Landfill Development and Ash Basin Closure,” August 2015. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 62 Amec Foster Wheeler, “Waste Inventory Analysis, Remaining Ash Volume Calculations for 1982 Basin,” December 8, 2015 (2015b). Dewberry & Davis, Inc., “Final Coal Combustion Waste Impoundment Dam Assessment Report, Site 7, 1982 Pond & 1964 Pond, Progress Energy Carolinas, Asheville, North Carolina”, Revised Final September 11, 2009. Duke Energy, “Asheville Steam Electric Generating Plant, Coal Ash Excavation Plan,” December 2016. Law Engineering, Inc. (Amec Foster Wheeler), “Stability Analysis of Downstream Slope, 1982 Ash Pond Dike,” September 30, 1992. MACTEC Engineering and Consulting, Inc. (Amec Foster Wheeler), “Geotechnical Exploration Data Report, Asheville FGD Project, Constructed Wetlands System,” October 18, 2004. MACTEC Engineering and Consulting, Inc. (Amec Foster Wheeler), “Report of Geotechnical Exploration, 1982/1964 Ash Pond Drainage Modification Project,” January 19, 2011. NCDENR Notice of Inspection Reports for 1964 Ash Pond Dam (BUNCO-097) dated April 30, 2010; May 6, 2011; February 22, 2012; April 19, 2013; and April1, 2014. NCDENR Notice of Inspection Reports for 1982 Ash Pond Dam (BUNCO-089) dated May 5, 2010; May 6, 2011; February 22, 2012; April 19, 2013; and, April1, 2014. S&ME, Inc. “1964 Ash Basin Dam Improvement Design – Appendix I – Slope Stability Analysis Discussion and Summary,” December 28, 2009. S&ME Inc., “Construction Repair Certification Report, 1964 Ash Basin Dam Improvements (Phase II), Progress Energy Asheville Plant”, December 18, 2012. S&ME, Inc., “Subsurface Investigation and Slope Stability Analysis of 1964 Ash Basin Dike,” December 28, 2009. Stantec, “Asheville Plant – Field Reconnaissance”, 2014. SynTerra Corp., “Comprehensive Site Assessment Report, Duke Energy Asheville Steam Electric Plant,” August 23, 2015 (2015a). SynTerra Corp., “Comprehensive Site Assessment Supplement 1, Duke Energy Asheville Steam Electric Plant,” August 31, 2016 (2016b). SynTerra Corp., “Corrective Action Plan, Part 1, Duke Energy Asheville Steam Electric Plant,” November 20, 2015 (2015b). SynTerra Corp., “Corrective Action Plan, Part 2, Duke Energy Asheville Steam Electric Plant,” February 19, 2016 (2016a). SynTerra Corp., “Drinking Water Well and Receptor Survey for Asheville Steam Electric Plant,” September 2014 (2014a). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 63 SynTerra Corp., “Seep Monitoring Report – June 2014 for Asheville Steam Electric Plant,” July 2014 (2014c). SynTerra Corp., “Supplement to Drinking Water Well and Receptor Survey for Asheville Steam Electric Plant,” November 2014 (2014b). Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 TABLES December 2016 Ta b l e 2 ‐1: Fe d e r a l CC R Ru l e Cl o s u r e Pl a n Re q u i r e m e n t s Su m m a r y an d Cr o s s Re f e r e n c e Ta b l e As h Ba s i n Si t e An a l y s i s an d Re m o v a l Pl a n ‐ As h e v i l l e St e a m El e c t r i c Ge n e r a t i n g Plant Du k e En e r g y No . D e s c r i p t i o n Corresponding Closure Plan Section i. N a r r a t i v e de s c r i p t i o n of ho w CC R un i t wi l l be cl o s e d (i n ac c o r d a n c e wi t h th i s se c t i o n ) All Chapters ii . I f cl o s u r e is th r o u g h th e re m o v a l of CC R fr o m th e un i t , de s c r i p t i o n of pr o c e d u r e s to re m o v e CC R an d de c o n t a m i n a t e CC R un i t (i n ac c o r d a n c e wi t h (c ) ) 7 ii i . If cl o s u r e by le a v i n g CC R in pl a c e , de s c r i p t i o n of fi n a l co v e r sy s t e m (i n ac c o r d a n c e wi t h (d ) ) , me t h o d s & pr o c e d u r e s us e d to in s t a l l fi n a l co v e r , an d al s o di s c u s s i o n of ho w fi n a l cover will achieve performance standards (in accordance wi t h (d ) ) NA iv . E s t i m a t e of ma x i m u m in v e n t o r y of CC R ev e r on si t e ov e r ac t i v e li f e of CC R un i t 3.1.2 v. E s t i m a t e of la r g e s t ar e a of CC R un i t ev e r re q u i r i n g a fi n a l co v e r (i n ac c o r d a n c e wi t h (d ) ) at an y ti m e du r i n g ac t i v e li f e of CC R un i t NA vi . S c h e d u l e fo r co m p l e t i o n of al l ac t i v i t i e s ne c e s s a r y to sa t i s f y cl o s u r e , in c l u d i n g es t i m a t e of ye a r in wh i c h al l cl o s u r e ac t i v i t i e s wi l l be co m p l e t e d . Su f f i c i e n t in f o r m a t i o n to de s c r i b e se q u e n t i a l steps of closure, including:12.1 a. O b t a i n i n g ap p r o v a l s an d pe r m i t s 10 b. D e w a t e r i n g an d st a b i l i z a t i o n ph a s e s 7 c. I n s t a l l a t i o n of fi n a l co v e r sy s t e m 7 d. E s t i m a t e d ti m e f r a m e s to co m p l e t e ea c h st e p / p h a s e 10 No t e : I f cl o s u r e ex c e e d s ti m e f r a m e s in (f ) ( 1 ) , cl o s u r e pl a n mu s t in c l u d e si t e sp e c i f i c in f o . / f a c t o r s / c o n s i d e r a t i o n s to su p p o r t ti m e ex t e n s i o n . Fe d e r a l Re g i s t e r Vo l . 80 No . 74 Pa r t 2 (A p r i l 17 , 20 1 5 ) / 4 0 CF R Pa r t 25 7 : En v i r o n m e n t a l Pr o t e c t i o n , Be n e f i c i a l Us e , Co a l Co m b u s t i o n Pr o d u c t s , CC R s , Co a l Co m b u s t i o n Wa s t e , Di s p o s a l , Hazardous Waste, Landfill, Surface Impoundments 40 CF R §2 5 7 . 1 0 2 (b ) ( 1 ) (i . ‐ vi ) Cl o s u r e Pl a n s fo r al l im p o u n d m e n t s sh a l l in c l u d e al l of th e fo l l o w i n g : December 2016 Ta b l e 2 ‐2: NC CA M A Cl o s u r e Pl a n Re q u i r e m e n t s Su m m a r y an d Cr o s s Re f e r e n c e Ta b l e As h Ba s i n Si t e An a l y s i s an d Re m o v a l Pl a n ‐ As h e v i l l e St e a m El e c t r i c Ge n e r a t i n g Pl a n t Du k e En e r g y No . D e s c r i p t i o n Corresponding Closure Plan Section 1 S i t e hi s t o r y an d hi s t o r y of si t e op e r a t i o n s , in c l u d i n g de t a i l s on th e ma n n e r in wh i c h co a l co m b u s t i o n re s i d u a l s ha v e be e n st o r e d an d di s p o s e d of hi s t o r i c a l l y . 3.1.1 2 E s t i m a t e d vo l u m e of ma t e r i a l co n t a i n e d in th e im p o u n d m e n t . 3.1.2 3 A n a l y s i s of th e st r u c t u r a l in t e g r i t y of di k e s or da m s as s o c i a t e d wi t h im p o u n d m e n t . 3.1.3 4 A l l so u r c e s of di s c h a r g e in t o th e im p o u n d m e n t , in c l u d i n g vo l u m e an d ch a r a c t e r i s t i c s of ea c h di s c h a r g e . 3.1.4 5 W h e t h e r th e im p o u n d m e n t is li n e d , an d , if so , th e co m p o s i t i o n th e r e o f . 3.1.5 6A su m m a r y of al l in f o r m a t i o n av a i l a b l e co n c e r n i n g th e im p o u n d m e n t as a re s u l t of in s p e c t i o n s an d mo n i t o r i n g co n d u c t e d pu r s u a n t to th i s Pa r t an d ot h e r w i s e av a i l a b l e . 3.1.6 1 Al l st r u c t u r e s as s o c i a t e d wi t h th e op e r a t i o n of an y co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t lo c a t e d on th e si t e . Fo r pu r p o s e s of th i s su b ‐su b d i v i s i o n , th e te r m "s i t e " me a n s th e la n d or wa t e r s wi t h i n th e pr o p e r t y bo u n d a r y of th e ap p l i c a b l e el e c t r i c ge n e r a t i n g st a t i o n . 3.2.1 2 Al l cu r r e n t an d fo r m e r co a l co m b u s t i o n re s i d u a l s di s p o s a l an d st o r a g e ar e a s on th e si t e , in c l u d i n g de t a i l s co n c e r n i n g co a l co m b u s t i o n re s i d u a l s pr o d u c e d hi s t o r i c a l l y by th e el e c t r i c ge n e r a t i n g st a t i o n an d di s p o s e d of th r o u g h tr a n s f e r to st r u c t u r a l fi l l s . 3.2.1 3 T h e pr o p e r t y bo u n d a r y fo r th e ap p l i c a b l e si t e , in c l u d i n g es t a b l i s h e d co m p l i a n c e bo u n d a r i e s wi t h i n th e si t e . 3.3 4 A l l po t e n t i a l re c e p t o r s wi t h i n 2, 6 4 0 fe e t fr o m es t a b l i s h e d co m p l i a n c e bo u n d a r i e s . 3.2.2 5 T o p o g r a p h i c co n t o u r in t e r v a l s of th e si t e sh a l l be se l e c t e d to en a b l e an ac c u r a t e re p r e s e n t a t i o n of si t e fe a t u r e s an d te r r a i n an d in mo s t ca s e s sh o u l d be le s s th a n 20 ‐fo o t in t e r v a l s . 3 . 3 6 Lo c a t i o n s of al l sa n i t a r y la n d f i l l s pe r m i t t e d pu r s u a n t to th i s Ar t i c l e on th e si t e th a t ar e ac t i v e l y re c e i v i n g wa s t e or ar e cl o s e d , as we l l as th e es t a b l i s h e d co m p l i a n c e bo u n d a r i e s an d co m p o n e n t s of as s o c i a t e d gr o u n d w a t e r an d su r f a c e wa t e r mo n i t o r i n g sy s t e m s . 3.2.3 7 A l l ex i s t i n g an d pr o p o s e d gr o u n d w a t e r mo n i t o r i n g we l l s as s o c i a t e d wi t h an y co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t on th e si t e . 3.3 8 A l l ex i s t i n g an d pr o p o s e d su r f a c e wa t e r sa m p l e co l l e c t i o n lo c a t i o n s as s o c i a t e d wi t h an y co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t on th e si t e . 3.3 1A de s c r i p t i o n of th e hy d r o g e o l o g y an d ge o l o g y of th e si t e . 4.1 2A de s c r i p t i o n of th e st r a t i g r a p h y of th e ge o l o g i c un i t s un d e r l y i n g ea c h co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t lo c a t e d on th e si t e . 4.2 3 Th e sa t u r a t e d hy d r a u l i c co n d u c t i v i t y fo r (i ) th e co a l co m b u s t i o n re s i d u a l s wi t h i n an y co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t lo c a t e d on th e si t e an d (i i ) th e sa t u r a t e d hy d r a u l i c co n d u c t i v i t y of an y ex i s t i n g li n e r in s t a l l e d at an im p o u n d m e n t , if an y . 4.3 4 Th e ge o t e c h n i c a l pr o p e r t i e s fo r (i ) th e co a l co m b u s t i o n re s i d u a l s wi t h i n an y co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t lo c a t e d on th e si t e , (i i ) th e ge o t e c h n i c a l pr o p e r t i e s of an y ex i s t i n g li n e r in s t a l l e d at an im p o u n d m e n t , if an y , an d (i i i ) th e up p e r m o s t id e n t i f i e d st r a t i g r a p h i c un i t un d e r l y i n g th e im p o u n d m e n t , in c l u d i n g th e so i l cl a s s i f i c a t i o n ba s e d up o n th e Un i f i e d So i l Cl a s s i f i c a t i o n Sy s t e m , in ‐pl a c e mo i s t u r e co n t e n t , pa r t i c l e si z e di s t r i b u t i o n , At t e r b e r g li m i t s , sp e c i f i c gr a v i t y , ef f e c t i v e fr i c t i o n an g l e , ma x i m u m dr y de n s i t y , op t i m u m mo i s t u r e co n t e n t , an d pe r m e a b i l i t y . 4.4 5A ch e m i c a l an a l y s i s of th e co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t , in c l u d i n g wa t e r , co a l co m b u s t i o n re s i d u a l s , an d co a l co m b u s t i o n re s i d u a l s ‐af f e c t e d so i l . 4.5 6 Id e n t i f i c a t i o n of al l su b s t a n c e s wi t h co n c e n t r a t i o n s de t e r m i n e d to be in ex c e s s of th e gr o u n d w a t e r qu a l i t y st a n d a r d s fo r th e su b s t a n c e es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e , in c l u d i n g al l la b o r a t o r y re s u l t s fo r th e s e an a l y s e s . 4.6 7 S u m m a r y ta b l e s of hi s t o r i c a l re c o r d s of gr o u n d w a t e r sa m p l i n g re s u l t s . 4.6 8 A ma p th a t il l u s t r a t e s th e po t e n t i o m e t r i c co n t o u r s an d fl o w di r e c t i o n s fo r al l id e n t i f i e d aq u i f e r s un d e r l y i n g im p o u n d m e n t s (s h a l l o w , in t e r m e d i a t e , an d de e p ) an d th e ho r i z o n t a l ex t e n t of ar e a s wh e r e gr o u n d w a t e r qu a l i t y st a n d a r d s es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e fo r a su b s t a n c e ar e ex c e e d e d . 4.7 9 Cr o s s ‐se c t i o n s th a t il l u s t r a t e th e fo l l o w i n g : th e ve r t i c a l an d ho r i z o n t a l ex t e n t of th e co a l co m b u s t i o n re s i d u a l s wi t h i n an im p o u n d m e n t ; st r a t i g r a p h y of th e ge o l o g i c un i t s un d e r l y i n g an im p o u n d m e n t ; an d th e ve r t i c a l ex t e n t of ar e a s wh e r e gr o u n d w a t e r qu a l i t y st a n d a r d s es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e fo r a su b s t a n c e ar e ex c e e d e d . 4.8 d. 1 An ac c o u n t of th e de s i g n of th e pr o p o s e d Cl o s u r e Pl a n th a t is ba s e d on th e si t e hy d r o g e o l o g i c co n c e p t u a l mo d e l de v e l o p e d an d in c l u d e s (i ) pr e d i c t i o n s on po s t ‐cl o s u r e gr o u n d w a t e r el e v a t i o n s an d gr o u n d w a t e r fl o w di r e c t i o n s an d ve l o c i t i e s , in c l u d i n g th e ef f e c t s on an d fr o m th e po t e n t i a l re c e p t o r s an d (i i ) pr e d i c t i o n s at th e co m p l i a n c e bo u n d a r y fo r su b s t a n c e s wi t h co n c e n t r a t i o n s de t e r m i n e d to be in ex c e s s of th e gr o u n d w a t e r qu a l i t y st a n d a r d s fo r th e su b s t a n c e es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e . 5.1 2 Pr e d i c t i o n s th a t in c l u d e th e ef f e c t s on th e gr o u n d w a t e r ch e m i s t r y an d sh o u l d de s c r i b e mi g r a t i o n , co n c e n t r a t i o n , mo b i l i z a t i o n , an d fa t e fo r su b s t a n c e s wi t h co n c e n t r a t i o n s de t e r m i n e d to be in ex c e s s of th e gr o u n d w a t e r qu a l i t y st a n d a r d s fo r th e su b s t a n c e es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e pr e ‐ an d po s t ‐cl o s u r e , in c l u d i n g th e ef f e c t s on an d fr o m po t e n t i a l re c e p t o r s . 5.2 3 A de s c r i p t i o n of th e gr o u n d w a t e r tr e n d an a l y s i s me t h o d s us e d to de m o n s t r a t e co m p l i a n c e wi t h gr o u n d w a t e r qu a l i t y st a n d a r d s fo r th e su b s t a n c e es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e an d re q u i r e m e n t s fo r co r r e c t i v e ac t i o n of gr o u n d w a t e r co n t a m i n a t i o n es t a b l i s h e d by Su b c h a p t e r L of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e . 5.3 Pa r t II . Pr o v i s i o n s fo r Co m p r e h e n s i v e Ma n a g e m e n t of Co a l Co m b u s t i o n Re s i d u a l s § 13 0 A ‐30 9 . 2 1 4 ( a ) ( 4 ) Cl o s u r e Pl a n s fo r al l im p o u n d m e n t s sh a l l in c l u d e al l of th e fo l l o w i n g : a. Fa c i l i t y an d co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t de s c r i p t i o n . – A de s c r i p t i o n of th e op e r a t i o n of th e si t e th a t sh a l l in c l u d e , at a mi n i m u m , al l of th e fo l l o w i n g : b. Si t e ma p s , wh i c h , at a mi n i m u m , il l u s t r a t e al l of th e fo l l o w i n g : Th e re s u l t s of gr o u n d w a t e r mo d e l i n g of th e si t e th a t sh a l l in c l u d e , at a mi n i m u m , al l of th e fo l l o w i n g : c. Th e re s u l t s of a hy d r o g e o l o g i c , ge o l o g i c , an d ge o t e c h n i c a l in v e s t i g a t i o n of th e si t e , in c l u d i n g , at a mi n i m u m , al l of th e fo l l o w i n g : December 2016 Ta b l e 2 ‐2: NC CA M A Cl o s u r e Pl a n Re q u i r e m e n t s Su m m a r y an d Cr o s s Re f e r e n c e Ta b l e As h Ba s i n Si t e An a l y s i s an d Re m o v a l Pl a n ‐ As h e v i l l e St e a m El e c t r i c Ge n e r a t i n g Pl a n t Du k e En e r g y No . D e s c r i p t i o n Corresponding Closure Plan Section e. A de s c r i p t i o n of an y pl a n s fo r be n e f i c i a l us e of th e co a l co m b u s t i o n re s i d u a l s in co m p l i a n c e wi t h th e re q u i r e m e n t s of Se c t i o n .1 7 0 0 of Su b c h a p t e r B of Ch a p t e r 13 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e (R e q u i r e m e n t s fo r Be n e f i c i a l Us e of Co a l Co m b u s t i o n By ‐Pr o d u c t s ) an d Se c t i o n .1 2 0 5 of Su b c h a p t e r T of Ch a p t e r 2 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e (C o a l Co m b u s t i o n Pr o d u c t s Ma n a g e m e n t ) . 6.1 f. Al l en g i n e e r i n g dr a w i n g s , sc h e m a t i c s , an d sp e c i f i c a t i o n s fo r th e pr o p o s e d Cl o s u r e Pl a n . If re q u i r e d by Ch a p t e r 89 C of th e Ge n e r a l St a t u t e s , en g i n e e r i n g de s i g n do c u m e n t s sh o u l d be pr e p a r e d , si g n e d , an d se a l e d by a pr o f e s s i o n a l en g i n e e r . 7.1, 7.2 g. A de s c r i p t i o n of th e co n s t r u c t i o n qu a l i t y as s u r a n c e an d qu a l i t y co n t r o l pr o g r a m to be im p l e m e n t e d in co n j u n c t i o n wi t h th e Cl o s u r e Pl a n , in c l u d i n g th e re s p o n s i b i l i t i e s an d au t h o r i t i e s fo r mo n i t o r i n g an d te s t i n g ac t i v i t i e s , sa m p l i n g st r a t e g i e s , an d re p o r t i n g re q u i r e m e n t s . 7.3 h. A de s c r i p t i o n of th e pr o v i s i o n s fo r di s p o s a l of wa s t e w a t e r an d ma n a g e m e n t of st o r m w a t e r an d th e pl a n fo r ob t a i n i n g al l re q u i r e d pe r m i t s . 8 i. A de s c r i p t i o n of th e pr o v i s i o n s fo r th e fi n a l di s p o s i t i o n of th e co a l co m b u s t i o n re s i d u a l s . If th e co a l co m b u s t i o n re s i d u a l s ar e to be re m o v e d , th e ow n e r mu s t id e n t i f y (i ) th e lo c a t i o n an d pe r m i t nu m b e r fo r th e co a l co m b u s t i o n re s i d u a l s la n d f i l l s , in d u s t r i a l la n d f i l l s , or mu n i c i p a l so l i d wa s t e la n d f i l l s in wh i c h th e co a l co m b u s t i o n re s i d u a l s wi l l be di s p o s e d an d (i i ) in th e ca s e wh e r e th e co a l co m b u s t i o n re s i d u a l s ar e pl a n n e d fo r be n e f i c i a l us e , th e lo c a t i o n an d ma n n e r in wh i c h th e re s i d u a l s wi l l be te m p o r a r i l y st o r e d . If th e co a l co m b u s t i o n re s i d u a l s ar e to be le f t in th e im p o u n d m e n t , th e ow n e r mu s t (i ) in th e ca s e of cl o s u r e pu r s u a n t to su b ‐su b d i v i s i o n (a ) ( 1 ) a . of th i s se c t i o n , pr o v i d e a de s c r i p t i o n of ho w th e as h wi l l be st a b i l i z e d pr i o r to co m p l e t i o n of cl o s u r e in ac c o r d a n c e wi t h cl o s u r e an d po s t ‐cl o s u r e re q u i r e m e n t s es t a b l i s h e d by Se c t i o n .1 6 2 7 of Su b c h a p t e r B of Ch a p t e r 13 of Ti t l e 15 A of th e No r t h Ca r o l i n a Ad m i n i s t r a t i v e Co d e an d (i i ) in th e ca s e of cl o s u r e pu r s u a n t to su b ‐su b d i v i s i o n (a ) ( 1 ) b . of th i s se c t i o n , pr o v i d e a de s c r i p t i o n of ho w th e as h wi l l be st a b i l i z e d pr e ‐ an d po s t ‐cl o s u r e . If th e co a l co m b u s t i o n re s i d u a l s ar e to be le f t in th e im p o u n d m e n t , th e ow n e r mu s t pr o v i d e an es t i m a t e of th e vo l u m e of co a l co m b u s t i o n re s i d u a l s re m a i n i n g . 9 j. A li s t of al l pe r m i t s th a t wi l l ne e d to be ac q u i r e d or mo d i f i e d to co m p l e t e cl o s u r e ac t i v i t i e s . 10 k. A de s c r i p t i o n of th e pl a n fo r po s t ‐cl o s u r e mo n i t o r i n g an d ca r e fo r an im p o u n d m e n t fo r a mi n i m u m of 30 ye a r s . Th e le n g t h of th e po s t ‐cl o s u r e ca r e pe r i o d ma y be (i ) pr o p o s e d to be de c r e a s e d or th e fr e q u e n c y an d pa r a m e t e r li s t mo d i f i e d if th e ow n e r de m o n s t r a t e s th a t th e re d u c e d pe r i o d or mo d i f i c a t i o n s ar e su f f i c i e n t to pr o t e c t pu b l i c he a l t h , sa f e t y , an d we l f a r e ; th e en v i r o n m e n t ; an d na t u r a l re s o u r c e s an d (i i ) in c r e a s e d by th e De p a r t m e n t at th e en d of th e po s t ‐cl o s u r e mo n i t o r i n g an d ca r e pe r i o d if th e r e ar e st a t i s t i c a l l y si g n i f i c a n t in c r e a s i n g gr o u n d w a t e r qu a l i t y tr e n d s or if co n t a m i n a n t co n c e n t r a t i o n s ha v e no t de c r e a s e d to a le v e l pr o t e c t i v e of pu b l i c he a l t h , sa f e t y , an d we l f a r e ; th e en v i r o n m e n t ; an d na t u r a l re s o u r c e s . If th e ow n e r de t e r m i n e s th a t th e po s t ‐cl o s u r e ca r e mo n i t o r i n g an d ca r e pe r i o d is no lo n g e r ne e d e d an d th e De p a r t m e n t ag r e e s , th e ow n e r sh a l l pr o v i d e a ce r t i f i c a t i o n , si g n e d an d se a l e d by a pr o f e s s i o n a l en g i n e e r , ve r i f y i n g th a t po s t ‐cl o s u r e mo n i t o r i n g an d ca r e ha s be e n co m p l e t e d in ac c o r d a n c e wi t h th e po s t ‐cl o s u r e pl a n . If re q u i r e d by Ch a p t e r 89 C of th e Ge n e r a l St a t u t e s , th e pr o p o s e d pl a n fo r po s t ‐cl o s u r e mo n i t o r i n g an d ca r e sh o u l d be si g n e d an d se a l e d by a pr o f e s s i o n a l en g i n e e r . Th e pl a n sh a l l in c l u d e , at a mi n i m u m , al l of th e fo l l o w i n g : 11 1A de m o n s t r a t i o n of th e lo n g ‐te r m co n t r o l of al l le a c h a t e , af f e c t e d gr o u n d w a t e r , an d st o r m w a t e r . 11 2 A de s c r i p t i o n of a gr o u n d w a t e r mo n i t o r i n g pr o g r a m th a t in c l u d e s (i ) po s t ‐cl o s u r e gr o u n d w a t e r mo n i t o r i n g , in c l u d i n g pa r a m e t e r s to be sa m p l e d an d sa m p l i n g sc h e d u l e s ; (i i ) an y ad d i t i o n a l mo n i t o r i n g we l l in s t a l l a t i o n s , in c l u d i n g a ma p wi t h th e pr o p o s e d lo c a t i o n s an d we l l co n s t r u c t i o n de t a i l s ; an d (i i i ) th e ac t i o n s pr o p o s e d to mi t i g a t e st a t i s t i c a l l y si g n i f i c a n t in c r e a s i n g gr o u n d w a t e r qu a l i t y tr e n d s . 11.1 l. A n es t i m a t e of th e mi l e s t o n e da t e s fo r al l ac t i v i t i e s re l a t e d to cl o s u r e an d po s t ‐cl o s u r e . 12.1 m. P r o j e c t e d co s t s of as s e s s m e n t , co r r e c t i v e ac t i o n , cl o s u r e , an d po s t ‐cl o s u r e ca r e fo r ea c h co a l co m b u s t i o n re s i d u a l s su r f a c e im p o u n d m e n t . 12.2 n. A de s c r i p t i o n of th e an t i c i p a t e d fu t u r e us e of th e si t e an d th e ne c e s s i t y fo r th e im p l e m e n t a t i o n of in s t i t u t i o n a l co n t r o l s fo l l o w i n g cl o s u r e , in c l u d i n g pr o p e r t y us e re s t r i c t i o n s , an d re q u i r e m e n t s fo r re c o r d a t i o n of no t i c e s do c u m e n t i n g th e pr e s e n c e of co n t a m i n a t i o n , if ap p l i c a b l e , or hi s t o r i c a l si t e us e . 6.2 § 13 0 A ‐30 9 . 2 1 2 ( b ) ( 3 ) No la t e r th a n 60 da y s af t e r re c e i p t of a pr o p o s e d Cl o s u r e Pl a n , th e De p a r t m e n t sh a l l co n d u c t a pu b l i c me e t i n g in th e co u n t y or co u n t i e s pr o p o s e d Cl o s u r e Pl a n an d al t e r n a t i v e s to th e pu b l i c . § 13 0 A ‐30 9 . 2 1 2 ( d ) Wi t h i n 30 da y s of it s ap p r o v a l of a Co a l Co m b u s t i o n Re s i d u a l s Su r f a c e Im p o u n d m e n t Cl o s u r e Pl a n , th e De p a r t m e n t sh a l l su b m i t th e Cl o s u r e Pl a n to th e Co a l As h Ma n a g e m e n t Co m m i s s i o n . No t e : Al t h o u g h it is no t ma n d a t e d by CA M A , Du k e En e r g y is su b m i t t i n g th i s Cl o s u r e Pl a n to th e No r t h Ca r o l i n a De p a r t m e n t of En v i r o n m e n t a l Qu a l i t y (f o r m e r l y NC D E N R ) to as s i s t th e de p a r t m e n t wi t h id e n t i f y i n g ar e a s wh e r e it s pe r m i t t i n g ac t i o n s will be crucial in allowing Du k e En e r g y to me e t it s st a t u t o r y de a d l i n e s . Se c u r i n g th e re q u i r e d pe r m i t ap p r o v a l s by Ma r c h 31 , 20 1 6 , wi l l al l o w Du k e En e r g y to ac h i e v e cl o s u r e of th e 19 8 2 As h Ba s i n an d me e t th e re q u i r e m e n t s of th e Mo u n t a i n En e r g y Ac t of 20 1 5 (S e s s i o n La w 2015 ‐110, Signed June 24, 20 1 5 ) , wh i c h re q u i r e s th a t th e as h ba s i n s be cl o s e d by Au g u s t 1, 20 2 2 . Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 FIGURES STILLING BASIN 1964 ASH BASIN 1982 ASH BASIN N DWG SIZE REVISION FOR DRAWING NO. TITLE FILENAME: DWG TYPE: JOB NO: DATE: SCALE:DES: DFTR: CHKD: ENGR: APPD: A F E D C B 2 3 4 5 7 86 4 5 7 8 9 106 A F C B 11"x17" ANSI C Environment & Infrastructure SEAL 321 DWG SIZE REVISION FOR DRAWING NO. TITLE FILENAME: DWG TYPE: JOB NO: DATE: SCALE:DES: DFTR: CHKD: ENGR: APPD: A F E D C B 2 3 4 5 7 86 4 5 7 8 9 106 A F C B 11"x17" ANSI C Environment & Infrastructure SEAL 321 NC GEOLOGY: C-247 NC ENG: F-1253 LICENSURE: FAX: (865) 671-6254 TEL: (865) 671-6774 KNOXVILLE, TN 37922 SUITE 300 2030 FALLING WATERS 12-12-2016 7810160620 DWG AS SHOWN DS MB APT APT Figure 1 Site Location Map.dwg 0 1 01 F I G U R E 1 FIGURE 1 ASHEVILLE PLANT SKYLAND, NORTH CAROLINA DUKE ENERGY ASHEVILLE PLANT SITE LOCATION MAP 01FIGURE 1 750'2250'1500'0' LEGEND APPROXIMATE DUKE ENERGY PROPERTY BOUNDARY APPROXIMATE BASIN BOUNDARIES SERVICE LAYER: CREDITS: DELORME STREET ATLAS, ESRI ARCMAP, : 2013 NATIONAL GEOGRAPHIC SOCIETY. CONCRETE RIM DITCH DECANT BASIN 1982 ASH BASIN 1964 ASH BASIN 1964 ASH BASIN LIMITS (APPROXIMATE) LAKE JULIAN SEPARATOR DIKE 1982 ASH BASIN DAM I - 2 6 STEAM PLANT DUCK POND 1982 ASH BASIN LIMITS (APPROXIMATE) LAKE JULIAN F R E N C H B R O A D R I V E R PROPERTY BOUNDARY EXISTING STILLING BASIN LAKE JULIAN DAM 1964 ASH BASIN DAM FORMER WETLAND AREA N ISSUE/REVISION DESCRIPTIONYREVDM ENG.APPR. CLIENT LOGO: REVIEWED BY: SCALE: DATUM: PROJECTION: TITLE: PROJECT: DATE: FIGURE NO. REVISION NO. PROJECT NO.: DRAWN BY: CLIENT: 2801 YORKMONT ROAD, SUITE 100 CHARLOTTE, NC 28208 TEL:(704) 357-8600 FAX: (704) 357-8638 LICENSURE: NC ENG: F-1253 NC GEOLOGY: C-247 Amec Foster Wheeler Environment & Infrastructure, Inc. AS NOTED 7810160620 NA 12/12/2016 WGS84 STATE PLANE 83 APT MB DUKE ENERGY PROGRESS BUNCOMBE COUNTY, NORTH CAROLINA SITE ANALYSIS AND REMOVAL PLAN DUKE ENERGY - ASHEVILLE STEAM ELECTRIC GENERATING PLANT BUNCOMBE COUNTY, NORTH CAROLINA LEGEND ASH POND LIMITS PROPERTY BOUNDARY FORMER WETLAND AREA SITE OVERVIEW AERIAL PLAN 2 NOTE: 1.AERIAL PHOTO DATED 10-2015 SOURCE BY GOOGLE EARTH PRO. 2.PROPERTY BOUNDARY OBTAINED FROM BUNCOMBE COUNTY GIS DATA AT http://BUNCOMBECOUNTY.ORG/MAP_ALL.HTML. I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 F R E N C H B R O A D R I V E R F R E N C H B R O A D R I V E R MAHO G A N Y R O A D LAKE JULIAN LAKE JULIAN MAH O G A N Y R O A D ABER D E E N D R DOUGLA S F I R A V E PEPP E R B U S H T R L NEW R O C K W O O D R D NE W R O C K W O O D R D N E W R O C K W O O D R D I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 EXISTING CONTOURS SEPARATOR DIKE CONCRETE RIM DITCH DECANT BASIN 1982 ASH BASIN 1964 ASH BASIN 1982 ASH BASIN LIMITS (APPROXIMATE) 1964 ASH BASIN LIMITS (APPROXIMATE) EXISTING OVERHEAD TRANSMISSION LINES EXISTING WETLAND DISCHARGE PIPE (REMOVED) EXISTING STILLING BASIN EXISTING 66" RCP PROPERTY BOUNDARY FRENCH BROAD RIVER LAKE JULIAN 500' COMPLIANCE BOUNDARY ASH STACK DUCK POND 1964 ASH BASIN DAM 1982 ASH BASIN DAM STEAM PLANT (2) 36" HDPE RIM DITCH SYSTEM DISCHARGE LINES (APPROXIMATE) (NOT IN USE) MSD SEWER LINE EXISTING FGD DISCHARGE LINE (ABANDONED) EXISTING 36" HDPE PRIMARY SPILLWAY EXISTING 36" RISER w/ 36" HDPE BARREL OUTLET STRUCTURE EXISTING PIPE 1982 BASIN PRIMARY SPILLWAY (ABANDONED) HISTORICAL 1964 PRIMARY SPILLWAY 30" CONC. PIPE (ABANDONED) EXISTING OUTLET STRUCTURE 1982 BASIN PRIMARY SPILLWAY (ABANDONED) MH-02 CPF S CPFS CPFS CPFS CPFS CPFS CPFS CPFS CPFS CPFS CPFS C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S C P F S EXISTING CENTER POND FILTER SYSTEM PUMP PAD EXISTING 60" RCP N LEGEND ASH BASIN LIMITS PROPERTY BOUNDARY 500' COMPLIANCE BOUNDARY CCR IMPOUNDMENT RELATED STRUCTURES 3ISSUE/REVISION DESCRIPTIONYREVDM ENG.APPR. CLIENT LOGO: REVIEWED BY: SCALE: DATUM: PROJECTION: TITLE: PROJECT: DATE: FIGURE NO. REVISION NO. PROJECT NO.: DRAWN BY: CLIENT: 2801 YORKMONT ROAD, SUITE 100 CHARLOTTE, NC 28208 TEL:(704) 357-8600 FAX: (704) 357-8638 LICENSURE: NC ENG: F-1253 NC GEOLOGY: C-247 Amec Foster Wheeler Environment & Infrastructure, Inc. AS NOTED 7810160620 NA 12/12/2016 WGS84 STATE PLANE 83 APT MB DUKE ENERGY PROGRESS BUNCOMBE COUNTY, NORTH CAROLINA SITE ANALYSIS AND REMOVAL PLAN DUKE ENERGY - ASHEVILLE STEAM ELECTRIC GENERATING PLANT BUNCOMBE COUNTY, NORTH CAROLINA NOTE: 1.EXISTING TOPOGRAPHY PROVIDED BY DUKE ENERGY DATED 10-22-2014 AND 2007 WITH UPDATES BY OTHERS DATED 11-09-2016, 9-22-2016, 7-27-2015. 2.PROPERTY BOUNDARY OBTAINED FROM BUNCOMBE COUNTY GIS DATA AT http://BUNCOMBECOUNTY.ORG/MAP_ALL.HTML. I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 F R E N C H B R O A D R I V E R F R E N C H B R O A D R I V E R MAHO G A N Y R O A D LAKE JULIAN LAKE JULIAN MAH O G A N Y R O A D ABER D E E N D R DOUGLA S F I R A V E PEP P E R B U S H T R L NEW R O C K W O O D R D NE W R O C K W O O D R D N E W R O C K W O O D R D R O S E T T A L N NE W R O C K W O O D R D I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 I N T E R S T A T E 2 6 EXISTING CONTOURS EXISTING ROAD CONCRETE RIM DITCH DECANT BASIN 1982 ASH BASIN 1964 ASH BASIN DUCK POND 1982 ASH BASIN LIMITS (APPROXIMATE) 1964 ASH BASIN LIMITS (APPROXIMATE) EXISTING PRIMARY SPILLWAY EXISTING OVERHEAD TRANSMISSION LINES EXISTING WETLAND DISCHARGE PIPE EXISTING STILLING BASIN EXISTING OUTLET STRUCTURE 1964 ASH POND EXISTING 66" RCP EXISTING 60" RCP PROPERTY BOUNDARY LAKE JULIAN F R E N C H B R O A D R I V E R F R E N C H B R O A D R I V E R N LEGEND ASH BASIN LIMITS BORE HOLE OBSERVATION WELL PIEZOMETER PROPERTY BOUNDARY BORING LOCATION MAP 1982 & 1964 ASH BASINS 4ISSUE/REVISION DESCRIPTIONYREVDM ENG.APPR. CLIENT LOGO: REVIEWED BY: SCALE: DATUM: PROJECTION: TITLE: PROJECT: DATE: FIGURE NO. REVISION NO. PROJECT NO.: DRAWN BY: CLIENT: 2801 YORKMONT ROAD, SUITE 100 CHARLOTTE, NC 28208 TEL:(704) 357-8600 FAX: (704) 357-8638 LICENSURE: NC ENG: F-1253 NC GEOLOGY: C-247 Amec Foster Wheeler Environment & Infrastructure, Inc. AS NOTED 7810160620 NA 12/12/2016 WGS84 STATE PLANE 83 APT MB DUKE ENERGY PROGRESS BUNCOMBE COUNTY, NORTH CAROLINA SITE ANALYSIS AND REMOVAL PLAN DUKE ENERGY - ASHEVILLE STEAM ELECTRIC GENERATING PLANT BUNCOMBE COUNTY, NORTH CAROLINA NOTE: 1.EXISTING TOPOGRAPHY PROVIDED BY DUKE ENERGY DATED 10-22-2014 AND 2007 WITH UPDATES BY OTHERS DATED 11-09-2016, 9-22-2016, 7-27-2015. 2.PROPERTY BOUNDARY OBTAINED FROM BUNCOMBE COUNTY GIS DATA AT http://BUNCOMBECOUNTY.ORG/MAP_ALL.HTML. 3.BORING LOCATIONS DETERMINED FROM COORDINATES INCLUDED ON DRILL LOGS WHERE AVAILABLE. 4.ADDITIONAL BORING LOCATIONS WERE BASED ON DATA PROVIDED BY DUKE ENERGY. 5.SOME PIEZOMETER / MONITORING WELL LOCATIONS ARE SUBJECT TO BE ABANDONED AS PART OF THE CLOSURE ACTIVITIES. Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Asheville Steam Electric Generating Plant Site Analysis and Removal Plan Revision 0 APPENDICES