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Home My WebLink AboutNC0003425_CAMA Assessment Report PART 1.1_201805264 DUKE ENERGY. May 26, 2017 Mr. S. Jay Zimmerman, Director Division of Water Resources North Carolina Department of Environmental Quality 1611 Mail Service Center Raleigh, North Carolina 27699-1611 Subject: Additional Site Assessment Required Roxboro Steam F lectric Plant W.H. Weatherspoon Power Plant Dear Mr. Zimmerman: Pau: Draov tch Sen or Vice -President E"nvironmentar, Health & Safety 526 South Church Street: Mail Code EC3XP Charlotte, North Carolina 28202 980-373.0408 On August 18, 2016, Duke Energy (Duke) submitted Work Plans for additional assessment activities at the Roxboro Steam Electric Plant (Roxboro) and W.H. Weatherspoon Power Plant (Weatherspoon). On November 23, 2016 (revised December 2, 2016) Duke received North Carolrna Department of Environmental Quality Division of Water Resources (DWR) approval to the Work Plans. On January 27, 2017 Duke requested a 60 day extension to the assessment reports whrch was approved by the Division on February 27, 2017 subsequently making the reports due on May 30, 2017. Rogers Energy Complex was included in the extension request but has since developed under a separate timeline. Attached you will find Additional Site Assessment Reports for each of the above facilities in accordance with the correspondence described above. This information is also being provided to the respective regional offices. If you have comments and/or questions, please direct them to Ed Sullivan at 980-373-3719. inc2Draovitch Senior Vice -President Environmental, Health & Safety Enclosure: Groundwater Assessment Reports- Roxboro Steam Electric Plant and W.H. Weatherspoon Power Plant Cc: Danny Smith - Raleigh Regional Office Supervisor (Roxboro) Trent Allen - Fayetteville Assistant Regional Office Supervisor (Weatherspoon) synTerra ASH BASIN EXTENSION IMPOUNDMENTS AND DISCHARGE CANALS ASSESSMENT REPORT ROXBORO STEAM ELECTRIC PLANT 1700 DUNNAWAY ROAD SEMORA, NORTH CAROLINA 27343 MAY 2017 PREPARED FOR DUKE ENERGY PROGRESS,, LLC RALEIGH, NORTH CAROLINA f ,DUKE ENERGY. PROGRESS Kathy Kathy Webb, NC LG 1328 Project Director 2r , SERE ��y;� t599 '�•, Craig Eady, NC LG 1599 Manager Kathy Kathy Webb, NC LG 1328 Project Director Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant - Semora, NC SynTerra TABLE OF CONTENTS SECTION EXECUTIVE SUMMARY PAGE ES -1 1.0 INTRODUCTION.........................................................................................................1-1 6-1 2.0 BACKGROUND............................................................................................................2-1 3-2 2.1 Site Description......................................................................................................... 2-1 2.2 Site History................................................................................................................. 2-1 2.3 WAB Southern Extension Impoundment and Discharge Canal ........................2-2 4-1 2.4 EAB Eastern Extension Impoundment and Discharge Canal ............................ 2-2 3.0 SITE GEOLOGY AND HYDROGEOLOGY............................................................3-1 4-1 3.1 Regional Geology......................................................................................................3-1 6-1 3.2 Site Geology............................................................................................................... 3-2 3.3 Regional Hydrogeology........................................................................................... 3-2 3.4 Site Hydrogeology.................................................................................................... 3-2 4.0 PROVISIONAL GROUNDWATER BACKGROUND CONCENTRATIONS. 4-1 4.1 Statistical Method......................................................................................................4-1 6-4 4.2 Background Concentrations.................................................................................... 4-1 5.0 SAMPLE COLLECTION..............................................................................................5-1 5.1 Wastewater Samples.................................................................................................5-1 5.2 Sediment and Sediment Core Samples.................................................................. 5-1 5.3 Groundwater Monitoring Well Installation..........................................................5-2 5.4 Groundwater Sampling........................................................................................... 5-4 6.0 ASH BASIN EXTENSION IMPOUNDMENTS AND DISCHARGE CANALS CHARACTERIZATION.............................................................................................. 6-1 6.1 WAB Southern Extension Impoundment and Discharge Canal Sample Results......................................................................................................................... 6-1 6.1.1 SEI Wastewater Data.......................................................................................... 6-1 6.1.2 SEI Discharge Canal Wastewater Data............................................................ 6-2 6.1.3 SEI Surficial and Core Sediment Data.............................................................. 6-2 6.1.4 SEI Discharge Canal Sediment and Core Sediment Data ............................. 6-3 6.1.5 SEI Groundwater Data....................................................................................... 6-4 6.1.6 SEI Discharge Canal Groundwater Data ......................................................... 6-4 Page i P: \ Duke Energy Progress.1026 \ 107. Roxboro Ash Basin GW Assessment Plan\ 33.Discharge Canal Assessment (EHS)\DC Assessment Report \Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant - Semora, NC SynTerra TABLE OF CONTENTS SECTION PAGE 6.2 EAB Eastern Extension Impoundment and Discharge Canal 1951 Aerial Photograph SampleResults........................................................................................................... 6-5 6.2.1 EEI Wastewater Data..........................................................................................6-5 1977 Aerial Photograph 6.2.2 EEI Discharge Canal Wastewater Data............................................................ 6-5 6.2.3 EEI Surficial and Core Sediment Data............................................................. 6-6 6.2.4 EEI Discharge Canal Sediment and Core Sediment Data ............................. 6-7 6.2.5 EEI Groundwater Data....................................................................................... 6-7 6.2.6 EEI Discharge Canal Groundwater Data ......................................................... 6-8 7.0 GROUNDWATER MODEL AND GEOCHEMICAL MODEL ............................ 7-1 7.1 Groundwater Model................................................................................................. 7-1 7.2 Geochemical Model.................................................................................................. 7-1 8.0 UPDATED SITE CONCEPTUAL MODEL.............................................................. 8-1 9.0 CONCLUSIONS AND RECOMMENDATIONS...................................................9-1 10.0 REFERENCES..............................................................................................................10-1 LIST OF FIGURES Figure 1-1 Site Location Map Figure 1-2 Site Layout Map Figure 2-1 1951 Aerial Photograph Figure 2-2 1964 Aerial Photograph Figure 2-3 1977 Aerial Photograph Figure 2-4 1993 Aerial Photograph Figure 2-5 2008 Aerial Photograph Figure 2-6 2016 Aerial Photograph Figure 2-7 Operational Flow Diagram Page ii P: \ Duke Energy Progress.1026 \ 107. Roxboro Ash Basin GW Assessment Plan\ 33.Discharge Canal Assessment (EHS)\DC Assessment Report \Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra LIST OF FIGURES (CONTINUED) Figure 5-1 Sample Locations Figure 5-2 Sample Locations - Southern Extension Impoundment and Western Discharge Canal Figure 5-3 Sample Locations -Eastern Extension Impoundment and Eastern Discharge Canal Figure 6-1 Isoconcentration Map - Boron in Bedrock Groundwater Figure 8-1 Generalized Water Level Map (April 2017) Figure 8-2 Site Cross-section Location Map Figure 8-3 Site Cross-section A -A' Figure 8-4 Site Cross-section B -B' LIST OF TABLES Table 4-1 Provisional Background Bedrock Groundwater Concentrations Table 5-1 CCR / Sediment Thickness Summary - Southern Extension Impoundment and Western Discharge Canal Table 5-2 CCR / Sediment Thickness Summary - Eastern Extension Impoundment and Eastern Discharge Canal Table 5-3 Well Construction Data Table 6-1 Wastewater Analytical Results - Southern Extension Impoundment and Western Discharge Canal Table 6-2 Sediment Analytical Results - Southern Extension Impoundment and Western Discharge Canal Table 6-3 SPLP Analytical Results - Southern Extension Impoundment Table 6-4 Groundwater Analytical Results - WAB, SEI and WDC Area Wells Table 6-5 Wastewater Analytical Results - Eastern Extension Impoundment and Eastern Discharge Canal Table 6-6 Sediment Analytical Results - Eastern Extension Impoundment and Eastern Discharge Canal Table 6-7 SPLP Analytical Results - Eastern Extension Impoundment Table 6-8 Groundwater Analytical Results - EAB, EEI and EDC Area Wells Table 8-1 Water Elevation Data - April 10, 2017 Page iii P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS)\DC Assessment Report \Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra LIST OF APPENDICES Appendix A NCDEQ Correspondence Appendix B NPDES Permit Development Fact Sheet Appendix C Well Construction Appendix C.1 Well Construction Logs Appendix C.2 Drillers Logs Appendix C.3 Well Development Logs Appendix D Sediment Logs Appendix D.1 Sediment Core Description Logs Appendix D. 2 Sediment Core Photos Appendix E Analytical Reports Appendix E.1 Waste Water Samples Appendix E.2 Sediment Samples Appendix E.3 Groundwater Samples Page iv P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra LIST OF ACRONYMS 2B NCDEQ/DWR Title 15, Subchapter 2B. Surface Water and Wetland NAVD 88 Standards 2L NCDEQ/DWR Title 15, Subchapter 2L. Groundwater Quality MDL Standards bgs Below ground surface CAMA Coal Ash Management Act CAP Corrective Action Plan CCR Coal Combustion Residuals CSA Comprehensive Site Assessment DFA Dry Fly Ash DEP Duke Energy Progress DO Dissolved Oxygen EEI Eastern Extension Impoundment FGD Flue Gas Desulfurization IMAC Interim Maximum Allowable Concentrations NAVD 88 North American Vertical Datum of 1988 MCL Federal Maximum Contaminant Level MDL Method Detection Limit NCAC North Carolina Administrative Code NCDEQ North Carolina Department of Environmental Quality (formerly NCDENR) NCDWR North Carolina Division of Water Resources NPDES National Pollution Discharge Elimination System NTU Nephelometric Turbidity Unit PBC Provisional Background Concentrations Plant/Site Roxboro Steam Electric Plant PLM Polarized Light Microscopy SCM Site Conceptual Model SEI Southern Extension Impoundment TDS Total Dissolved Solids UTL Upper Tolerance Limit USEPA United States Environmental Protection Agency Page v P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra EXECUTIVE SUMMARY In a letter dated July 8, 2016, the North Carolina Department of Environmental Quality (NCDEQ) Division of Water Resources (DWR) requested that Duke Energy assess the distribution of coal combustion residual (CCR) at confirmed and potential disposal sites that included areas at the Roxboro Steam Electric Plant. The purpose of the assessment is to determine if potential coal ash constituents in the ash basin extension impoundments and their discharge canals may be an additional contributing source to groundwater. The assessment activities were conducted in the summer of 2016 through March 2017 and included: 167 The collection and characterization of wastewater and sediment samples from each of the extension impoundments and their related discharge canals. 167 The installation of groundwater monitoring wells within each hydrogeologic unit, as applicable, at strategic locations in the vicinity of the extension impoundments and their related discharge canals. 167 The collection of groundwater samples from the newly installed and existing groundwater monitoring wells to evaluate groundwater flow characteristics and groundwater quality related to the extension impoundments and discharge canals. West Ash Basin Extension Impoundment and Discharge Canal Assessment Water in the extension impoundment and discharge canal are subject only to NPDES discharge permit requirements to the heated water discharge pond via Outfall 002 and are not considered waters of the state. In this report, analytical results are compared to North Carolina 2L or IMAC standards for informational purposes to assess potential source contribution to groundwater. The analytical results indicate arsenic, boron, cobalt, iron, manganese, thallium and vanadium are greater than 2L or IMAC within the impoundment and the discharge canal. In the discharge canal, the constituents increased in concentration downstream from the filter dike towards NPDES Outfall #002. 07 Ash thickness from 1 to 5 feet was observed within the impoundment, which was greatest near the filter dike, and from 1 to 1.5 feet within the discharge canal. P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 17 Analytical results for the sediment samples, as compared to USEPA RSLs for Soil for Protection of Groundwater (May 2016), revealed arsenic, barium, copper, lead, mercury, selenium, and vanadium concentrations were greater than the RSL in one or more sediment samples within the impoundment and the discharge canal. 101 With the exception of antimony, arsenic, selenium and thallium in the sediment samples, the SPLP analysis for sediment samples are consistent with SPLP analysis of soil, including background locations, presented in the CSA. 07 One new groundwater monitoring well, MW-26BR, was installed on the eastside of the impoundment to support existing wells, CW -04 and MW-04BR, and three new groundwater monitoring wells, MW-31BR through MW-33BR, were installed at strategic locations along the discharge canal to support existing wells, MW-07BR, MW-08BR, and MW -12, to evaluate groundwater conditions in the upper most bedrock aquifer. 101 One groundwater sampling event from the new and pertinent existing wells indicate that several constituents were detected above the 2L or IMAC including total chromium, iron, manganese, sulfate, TDS, and vanadium. Boron was not detected above the method detection limit. With the exception of total chromium in MW-33BR and sulfate and TDS in MW-25BR, none of the detected constituents were above the provisional background concentrations. 167 With the detection of a few constituents above 2L or IMAC and provisional background concentrations and the lack of boron suggests the impoundment and discharge canal has not impacted the groundwater in the upper bedrock aquifer. East Ash Basin Extension Impoundment and Discharge Canal Assessment 17 Water in the extension impoundment and discharge canal are part of the ash basin and are not considered waters of the state. The water will be subject to NPDES discharge permit requirements to the intake canal via proposed Outfall #001 which is currently under regulatory review. In this report, analytical results are compared to North Carolina 2L or IMAC standards for informational purposes to assess potential source contribution to groundwater. The analytical results from water samples in the impoundment and discharge canal indicated boron, iron, manganese and vanadium concentrations are greater than 2L or IMAC with no apparent trend with the exception of greater boron concentrations near the confluence of the discharge canal and the impoundment. P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra ,67 Ash thickness from <1 to 20 feet was observed within the impoundment, which was greatest near the separator dike, and from <0.5 to 1 feet within the discharge canal, which was greatest near the confluence of the impoundment and the discharge canal. ,67 Analytical results for the sediment samples, as compared to USEPA Regional Screening Levels (RSLs) for Soil for Protection of Groundwater (May 2016), revealed antimony, arsenic, barium, copper, selenium, and vanadium concentrations were greater than the RSL in one or more surficial and core sediment samples within the impoundment and the discharge canal. 167 With the exception of antimony and thallium in the deep sediment samples from the impoundment, the SPLP analysis for sediment samples are consistent with SPLP analysis of soil, including background locations, presented in the CSA. 167 Three new groundwater monitoring wells, MW-23BR through MW-25BR, were installed around the impoundment to support existing wells, MW-17BR and MW-20BRL, and four new groundwater monitoring wells, MW-27BR through MW-30BR, were installed at strategic locations along the discharge canal to evaluate groundwater conditions in the upper most bedrock aquifer. 167 One groundwater sampling event from the new and pertinent existing wells indicate that several constituents were detected above the 2L or IMAC including total chromium, iron, manganese, TDS, and vanadium. Boron was not detected above the method detection limit. With the exception of total chromium and TDS in MW-25BR, none of the detected constituents were above the provisional background concentrations. H Boron was not detected in any of the groundwater samples suggesting the ash and wastewater present in the impoundment and the discharge canal has not impacted the groundwater in the upper bedrock aquifer. Based on the findings of the extension impoundment and discharge canal assessment activities, the following recommendations and observations are offered: 07 Additional monitoring of the impoundment and discharge canal wells is recommended to confirm the initial constituent concentrations. P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra ,67 Future groundwater flow and transport modeling and geochemical modeling will need to incorporate additional data to evaluate the impoundments and discharge canals. 17 No substantive changes to previous site conceptual model or previously predicted migrations of constituents from the ash basins were observed. ,67 Extend the compliance boundary to include the impoundments and related discharge canals per the 'Proposed Waste and Compliance Boundary" submitted by Duke Energy on August 19, 2016 in response to the Division of Water Resources July 8, 2016 request. P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 1.0 INTRODUCTION Duke Energy Progress, LLC (Duke Energy, DEP) owns and operates the Roxboro Steam Electric Plant (the Roxboro Plant, Plant or Site) located at 1700 Dunnaway Road in Semora, Person County, North Carolina (Figure 1-1). The Roxboro Plant is located on approximately 6,095 acres between McGhees Mill Road to the east and Hyco Lake, formed from the impoundment of the Hyco River, to the west. The Site is developed with the power plant structures, coal ash management areas and associated discharge canals (Figure 1-2). In 2014, the North Carolina General Assembly passed the Coal Ash Management Act (CAMA) which required owners of a coal combustion residuals (CCR) surface impoundment to conduct detailed site assessments. Results of CAMA related site assessments are documented in the following reports: 167 Comprehensive Site Assessment Report - Roxboro Steam Electric Plant (SynTerra, September 2, 2015). 167 Corrective Action Plan Part 1- Roxboro Steam Electric Plant (SynTerra, December 1, 2015). 167 Corrective Action Plan Part 2 - Roxboro Steam Electric Plant (SynTerra, February 29, 2016); and 101 Comprehensive Site Assessment Supplement 1- Roxboro Steam Electric Plant (SynTerra, August 1, 2016). In a letter dated July 8, 2016, the North Carolina Department of Environmental Quality (NCDEQ) Division of Water Resources (DWR) requested that Duke Energy provide data and conduct additional site assessment as needed to characterize CCR materials in areas that could contain potential source material that could impact groundwater (Appendix A). The request encompassed the West Ash Basin (WAB) southern extension impoundment (SEI) and associated discharge canal (WDC) and the East Ash Basin (EAB) eastern extension impoundment (EEI) and associated discharge canal (EDC). An assessment of water, sediment and groundwater of the EEI and a preliminary assessment of groundwater for the SEI were reported in the CSA Supplement I (SynTerra, August, 2016). The purpose of this assessment is to determine if potential coal ash constituents in the ash basin extension impoundments and their discharge canals may be a contributing source to groundwater. Page 1-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 2.0 BACKGROUND 2.1 Site Description The Roxboro Plant is located approximately 10 miles northwest of the City of Roxboro, NC. The Plant is located on approximately 6,095 acres between McGhees Mill Road to the east; Concord-Ceffo Road to the south; Semora Road to the west and Hyco Lake to the north. The Site is developed with the power plant structures, ash management areas and associated canals. The power plant structures are located primarily on the north side of the Site near the Hyco Lake and the ash management areas are located generally south of the power plant buildings. Land beyond the ash management areas to the east, south and west are wooded and transected by transmission lines. Hyco Lake borders the Site to the west and north. The approximate size of the combined ash basins is 220 acres with a total estimated ash inventory in both ash basins of 19,500,000 tons. The landfill ash inventory in the lined and unlined landfills is estimated to be 7,320,000 tons. Ash fill areas, including the structural fill under the gypsum pad, contain an estimated 7,800,000 tons. The total estimated CCR at the Roxboro facility is approximately 34,620,000 tons (https://www.duke-energy.com/pdfs/duke-energy-ash-metrics.pdf, updated June 2, 2016). The East Ash Basin is covered with vegetation and ponded water outside of the landfill footprint and the West Ash Basin has some grass cover and ponded water, mostly along the southern and eastern edges of the basin. 2.2 Site History A 1951 aerial photograph shows the Site consisting of a combination of agricultural land, rural residential, and woodlands prior to the impoundment of the Hyco River (Figure 2-1). By 1964, clearing operations for the Plant and construction of the main dam for the East Ash Basin had begun (Figure 2-2). The Plant began operations in 1966 as a coal-fired electrical generating station with additional generating units added in 1968, 1973, and 1980, with a combined electric generating capacity of 2,422 megawatts. CCRs have historically been managed at the Plant's two on-site ash basins: the semi- active East Ash Basin, which began operations from the mid-1960s, and the active West Ash Basin, which started operations from the early 1970s. CCRs were initially deposited in the EAB by hydraulic sluicing operations until the Plant was modified for dry fly ash (DFA) handling in the 1980s. An unlined landfill was constructed on top of the East Ash Basin for the placement of the DFA. A lined landfill was constructed in phases over the unlined landfill beginning in 2004. Most of the fly ash material produced at the facility is currently collected by dry handling operations and are Page 2-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra disposed within the lined landfill or transported offsite for beneficial reuse. The WAB was constructed in 1973 and still receives bottom ash by hydraulic sluicing methods. 2.3 WAB Southern Extension Impoundment and Discharge Canal The West Ash Basin was created in 1973 with the construction of an earthen dam (main dam) in a former stream channel to the southwest of the main plant. Figure 2-3 depicts the configuration of the WAB from a 1977 aerial photograph. In 1986, the main dam was raised 13 feet and a series of dikes (Dikes #1 through 4) and a discharge canal were constructed to increase the storage capacity of the WAB and modify the circulation pattern to increase ash settling time. The rock filter dike (Dike #1), constructed of rock fill with a sand filter blanket, was installed at the southern end of the WAB to create a secondary settling basin and to isolate the major portion of the ash basin, separating the SEI from the WAB. The SEI is located south of the filter dike (Dike #1) and is comprised of several "fingers" encompassing approximately 38.5 acres. The SEI has likely received ash from the WAB before the rock filter dike was constructed. Dikes #2, 3, and 4 were placed in topographic low areas along the excavated discharge canal on the west side of the WAB. The dikes were constructed by end -dumping soil fill from the excavated discharge canal and were supported with stone berms (buttresses), approximately 20 to 30 feet thick, on the downstream side of the dikes. The configuration of the WAB with the filter dike and the discharge canal as depicted in 1993 is shown in Figure 2-4. By 2008, the flue gas desulfurization lagoons were constructed within the WAB (Figure 2- 5) and the area has remained similar to present day (Figure 2-6). Drainage of the WAB and additional waste streams across the site are directed to the western discharge canal. The discharge canal receives waste streams from various on- site sources including: WAB effluent from bottom ash sluicing; landfill drainage and runoff from the EAB lined landfill; storm water runoff from the two ash basins; discharge from the Flue Gas Desulfurization Pond treatment process; cooling tower blowdown; domestic sewage treatment plant discharge; and surface water runoff (Figure 2-7). Effluent from the discharge canal passes through NPDES Internal Outfall #002 with discharge into the heated water discharge pond, which ultimately flows into Hyco Lake through NPDES Outfall# 003. 2.4 EAB Eastern Extension Impoundment and Discharge Canal The East Ash Basin was originally developed in 1964 with the construction of an earthen dam, to the southeast of the main plant, in a former stream channel (Figure 2-2). A discharge canal from the EAB was constructed as part of the original ash basin development and provided direct discharge of ash basin water and secondary surface water runoff from adjacent streams to the intake canal of the Hyco Lake (Figure 2-3). Page 2-2 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra The discharge was initially regulated under NPDES Permit #0003425 through internal Outfall #001. In 1994, the NCDEQ (former NC Department of Environment and Natural Resources (NCDENR)) no longer required discharge from the canal to be monitored under NPDES regulations. The former outfall location is currently under consideration for reinsertion into the NPDES permit. The NPDES Permit #0003425 fact sheet is provided in Appendix B. In the mid-1980s, an earthen separator dike was constructed on the eastern portion of the EAB to allow development of the overlying unlined landfill. The separator dike formed a barrier separating the EAB from the discharge canal and a portion of the former basin, creating the 9.4 acre eastern extension impoundment (Figure 2-4). Historical information indicates the EEI received ash directly through sluicing. A lined landfill was constructed in phases over the unlined landfill beginning in 2004 and can be seen in a 2008 aerial photograph (Figure 2-5). The final phase (Phase 6) of the lined landfill is currently used to handle DFA with the current configuration shown in Figure 2-6. Page 2-3 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 3.0 SITE GEOLOGY AND HYDROGEOLOGY The Roxboro Plant is situated in the eastern Piedmont Region of north -central North Carolina. The Piedmont is characterized by well-rounded hills and rolling ridges cut by small streams and drainages. Elevations in the area of the Roxboro Plant range between 410 feet above mean sea level (msl) during full pool at Hyco Lake to 570 feet msl near the Dunnaway Road and McGhees Mill Road intersection southeast of the Plant. 3.1 Regional Geology Geologically, the Site is located near the contact of two regional geologic zones: the Inner Piedmont zone and the Carolina zone. Both zones are generally comprised of igneous and metamorphosed igneous and sedimentary rocks of Paleozoic age. In general, the rocks are highly fractured and folded and have been subjected to long periods of physical and chemical weathering. The origination, genesis, and characteristics of the rocks of the region have been the focus of detailed study by researchers for many years. These investigations have resulted in a number of interpretations and periodic refinements to the overall geological model of the region. Rocks of the region, except where exposed in road cuts, stream channels, and steep hillsides, are covered with unconsolidated material formed from the in-situ chemical and physical breakdown of the bedrock. This unconsolidated material is referred to as saprolite or residuum. Direct observations at the Site confirm the presence of saprolite, developed above the bedrock, which is generally 10 to 30 feet thick. The residuum extends from the ground surface (soil zones) downward, transitioning through a zone comprised of unconsolidated silt and sand, downward through a transition zone of partially weathered rock in a silt/sand matrix, down to the contact with competent bedrock. The Geologic Map of North Carolina (1985) places the rocks of the Plant area in the Charlotte Terrane: a belt of metamorphic rock trending generally southwest to northeast characterized by strongly foliated felsic mica gneiss and schist and metamorphosed intrusive rocks. The rocks of the area near the Plant are described as biotite gneiss and schist with abundant potassic feldspar and garnet, and interlayered and gradational with calcic -silicate rock, sillimanite-mica schist and amphibolite. The gneiss contains small masses of granite rock. The felsic mica gneiss of the Charlotte Terrane is described as being interlayered with biotite and hornblende schist. Later mapping generally confirms these observations and places the Roxboro Plant near the contact between the Inner Piedmont zone, characterized by the presence of biotite gneiss and schist, and the Charlotte Belt (or Charlotte Terrane), characterized by felsic Page 3-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra mica gneiss (USGS, 2007). A detailed description of the regional geology is presented in Section 5.1 of the CSA Report (SynTerra, September 2015). 3.2 Site Geology The Site is underlain by crystalline metamorphic rock, predominately gneiss. Biotite gneiss of the Inner Piedmont, felsic mica gneiss of the Charlotte and Minton Belts, and granitic gneiss of the Eastern Slate Belt were observed in rock cores collected at monitoring well locations. Field observations determined that biotite gneiss was more common in the north/northwest portion of the Site, felsic gneiss in the central portion, and a very hard granitic gneiss or granite in the south southeastern portion of the Site. 3.3 Regional Hydrogeology Groundwater within the Site area exists under unconfined, or water table, conditions within the residuum and/or saprolite zone and in fractures and joints of the underlying bedrock. The water table and bedrock water -bearing zones are interconnected. The saprolite, where saturated thickness is sufficient, acts as a reservoir for supplying groundwater to the fractures and joints in the bedrock. Shallow groundwater generally flows from local recharge zones in topographically high areas, such as ridges, toward groundwater discharge zones, such as stream valleys. Ridge and topographic high areas serve as groundwater recharge zones, and groundwater flow patterns in recharge areas tend to develop a somewhat radial pattern from the center of the recharge area outward toward the discharge areas and are expected to mimic surface topography. 3.4 Site Hydrogeology The position, geometry, topography, and hydrogeologic character of the ash basins, the former stream valleys to the Hyco River in which the basins were constructed, and Hyco Lake are the primary influences on groundwater flow and constituent transport at the Site. The former natural drainage features generally trend southeast to northwest across the site. The ash basins are separated by a northwest -southeast trending topographic ridge. Groundwater flow across the site is generally from upland areas south and southeast (recharge areas) toward Hyco Lake which is situated to the north/northwest. Localized areas of groundwater discharge to surface water occur from the two ash basins and the topographic ridge separating the basins. Further influences to groundwater flow include the earthen impoundments (dams and separator dikes) creating the basins; the intake canal (north of the EAB); the discharge canals; and the heated water discharge pond. Page 3-2 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra Based on the CSA investigation, the groundwater system in the natural materials (alluvium, soil, soil/weathered bedrock, and bedrock) at Roxboro is consistent with the Piedmont regolith -fractured rock system and is an unconfined, connected system of flow layers. Groundwater is rarely present in the shallow zones, can be present in the transition zone, and is typically present in fractures within the competent bedrock, with water bearing fractures decreasing with depth. Page 3-3 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 4.0 PROVISIONAL GROUNDWATER BACKGROUND CONCENTRATIONS Statistical analyses were conducted on groundwater data representative of locations that have not been influenced by coal ash constituents or other significant anthropogenic sources. Statistical methodology and results are presented in the following subsections. 4.1 Statistical Method Natural background concentrations for constituents within bedrock groundwater at the Site were determined to assess the potential impact of the impoundments and discharge canals on downgradient groundwater. Natural background concentrations for the transition zone were not evaluated as part of this assessment since the transition zone in the vicinity of the impoundments and the discharge canals is unsaturated (i.e., dry). Provisional background concentrations were determined for each constituent by calculating the upper tolerance limit (UTL) using a dataset consisting of sample results from bedrock background wells BG-1BR, MW-10BR, MW-13BR, MW-14BR, MW-15BR, MW-16BR, MW-17BR, MW-18BR and MW-19BRL. UTLs represent values in which a specified proportion (e.g., 95 percent) of a background dataset will fall below with a specified level of confidence (e.g., 95 percent). UTLs were calculated following the procedures outlined in the revised draft of Duke Energy's Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities (submitted January 2017) and in accordance with conditional approval provided in NCDEQ's response dated April 28, 2017. 4.2 Background Concentrations UTLs representing natural background concentrations for constituents within bedrock groundwater at the Site are provided in Table 4-1. UTLs for the chromium (VI), chromium (total), cobalt, iron, manganese, TDS, radium and vanadium are greater than the applicable regulatory standard, while UTLs for arsenic, barium, chloride, copper, nickel, sulfate, uranium and zinc are below the applicable regulatory standard. UTLs could not be calculated for constituent datasets consisting of fewer than two detectable concentrations which include: antimony, beryllium, boron, cadmium, lead, mercury, selenium and thallium. Page 4-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 5.0 SAMPLE COLLECTION Aqueous and solid media sampling was performed to determine presence or absence of CCR in the extension impoundments and discharge canals at the Roxboro Plant. SynTerra followed the sampling procedures as outlined in the Ash Basin Extension Impoundments and Discharge Canals Assessment Work Plan (Work Plan) (SynTerra, August 2016). Site wide sample locations are indicated on Figure 5-1. Figure 5-2 and Figure 5-3 focus on the impoundments and discharge canals. NCDEQ conditionally approved the Work Plan in November 2016 (NCDEQ, November 23, 2016). The main caveat by NCDEQ included additional monitoring wells to be installed in each water -bearing hydrostratigraphic unit at a nested well location southwest of existing well MW-12BR. The proposed well cluster location is indicated as MW -33. 5.1 Wastewater Samples As detailed in the Work Plan, grab water samples from the impoundments and discharge canals were collected directly into sample bottleware provided by the analytical laboratory. For shallow water samples (with a SW or S designation), the sample was collected by gently lowering lab provided bottleware into the water until a portion of the mouth was just below the water surface. Bottleware containing a preservative (e.g., acid) were filled with the grab water sample collected in bottleware that did not contain a preservative. Water samples were collected from a boat or samplers standing on the shoreline depending upon the sampling location and accessibility. For deeper water samples, a peristaltic pump with weighted tubing was used to sample at depth, typically approximately 2 feet above the bottom of the impoundment/discharge canal. New tubing was used between each sample location. Samples were analyzed for CAMA parameters as outlined in the Work Plan. 5.2 Sediment and Sediment Core Samples Sediment samples and sediment cores were collected from the impoundments and discharge canals by hand or manually pushing a clear acetate sleeve into the sediment to refusal. Sample locations were accessed by boat or samplers standing on the shoreline depending on sampling location and accessibility. Sediment samples were analyzed for parameters as outlined in the Work Plan. SynTerra collected sediment cores from the SEI and the EEI using direct push methods by a barge mounted GeoProbe or manually with the clear acetate sleeves. Visual inspection of sediment samples and sediment cores identified the presence of coal ash in the impoundments and their corresponding discharge canals. A summary of Page 5-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra the ash - sediment thickness within the impoundments and the discharge canals are provided in Table 5-1 (SEI and WDC) and Table 5-2 (EEI and EDC). Sediment core descriptions and photos are located in Appendix D. 5.3 Groundwater Monitoring Well Installation Four groundwater monitoring wells were installed in June 2016 to assess bedrock groundwater quality associated with the impoundments (Figure 1-2). MW-23BR, MW- 24BR and MW -25 were installed at strategic locations associated with the EEI to support existing wells, MW-17BR and MW-20BRL to evaluate groundwater conditions in the upper bedrock. MW-26BR was installed east and upgradient of the SEI to support existing wells, CW -04 and MW-04BR, to evaluate groundwater quality in the upper bedrock. Saturated conditions were not observed in the saprolite and/or transition zones around the impoundments; therefore, only bedrock wells were installed. Boring and well installation details were presented in the CSA Supplement (SynTerra, August 1, 2016). Well construction logs, drillers' logs and well development logs for the four impoundment wells are provided in Appendix C. In February 2017, MW-23BR was replaced due to elevated pH conditions in groundwater samples collected from the well. MW-23BRR was installed approximately 25 feet northeast of MW-23BR by Geologic Exploration (GeoEx) of Statesville, NC using air hammer drilling techniques. A water bearing fracture zone greater than 1.0 gpm was determined from 197 to 203 feet bgs, even though the fracture zone in MW-23BR was observed at 126 feet bgs. The replacement well, MW-23BRR, was drilled to a total depth of 204 feet bgs with a 10 -foot pre -packed screen set at 194-204 feet bgs. The depth to water in MW-23BRR was determined to be 3.99 feet bgs, whereas the depth to water in MW-23BR was indicated at 46.72 feet bgs, as measured on April 10, 2017. Therefore, the water bearing fracture zone in MW-23BRR is under greater hydrostatic head consistent to artesian conditions demonstrated at nearby MW-20BRL. The boring log with lithologic descriptions and well information for MW-23BRR is included in Appendix C. Seven groundwater monitoring wells were installed to assess groundwater quality associated with the impoundment discharge canals. The wells were installed in February 2017 using air hammer drilling techniques in accordance with the Work Plan. During drilling, unsaturated conditions were observed in the saprolite/transition zones at each location, leading to the installation of bedrock wells without the accompaniment of a shallow or transition zone well. Bedrock monitoring wells were installed to the first measureable water bearing fracture (> 1 gpm) in the bedrock, similar to the previous extension impoundment investigation conducted in June 2016. Page 5-2 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra Monitoring wells MW-27BR through MW-30BR were installed at strategic locations associated with the EEI discharge canal (Figure 1-2). MW-27BR is located northeast of the EAB and west of the EDC, in an area previously used as a soil borrow pit. The well is screened from 65 - 75 feet bgs to intersect a bedrock fracture observed at 70 feet bgs. MW-28BR, MW-29BR and MW-30BR are located east of the EDC. MW-28BR is screened from 124 -134 feet bgs to monitor a bedrock fracture zone observed at 127 -128 feet bgs. During drilling of MW-29BR, a water bearing fracture was observed at 83 feet bgs. The borehole was extended one foot and a well was installed at the bottom of the borehole, screened from 74 - 84 feet bgs. At MW-30BR, a water bearing fracture, producing more than five gallons per minute, was observed from 136 -138 feet bgs. MW-30BR was installed from 130 -140 bgs to monitor the fracture zone. Monitoring wells MW-31BR through MW -33 were installed at strategic locations associated with the SEI discharge canal. MW-31BR is screened from 68 - 78 feet bgs in granite gneiss to monitor a water bearing fracture observed at 70 feet bgs. MW-32BR and MW-33BR were installed significantly deeper in comparison to MW-31BR. MW- 32BR was installed from 250 - 260 feet bgs to capture a fracture observed at 257 feet bgs in granite gneiss. No significant water bearing fractures were observed in MW-32BR prior to 257 feet bgs. Equally for MW-33BR, no significant water bearing fractures were observed in the bedrock to a depth of 300 feet bgs based on field observations during drilling. To aid in screen placement in MW-33BR, packer tests were conducted throughout the borehole to locate a suitable water bearing zone. A double packer assembly with an approximate 15 foot screen was used. Based on the packer test results, a water bearing zone was determined from 284 - 299 feet bgs, though the yield was observed to be low (< 1 gpm). Therefore, a 15 foot screen was installed from 283 - 298 feet bgs in MW-33BR to evaluate the fracture zone. Each well was developed for minimum of two hours in accordance with Work Plan. Well construction logs, drillers' logs and well development logs are provided in Appendix C. During the February 2017 assessment activities, the background monitoring well, BG- 1BRL was replaced due to elevated pH conditions with very low yield observed in the well. The BG-01BRL borehole was initially installed on February 2016 and completed on March 2016 by Cascade Drilling Company (Cascade). Upon completion of boring installation and packer testing, no water bearing fractures were observed from 200 to 300 feet below ground surface (320 feet to 200 feet NAVD 88). With the Woodland Elementary School well reported at a total depth of 280 below ground surface (260 feet NAVD 88), a 10 -foot pre -packed screen was placed within a 30 -foot sand pack (252 feet to 220 feet NAVD 88) to intercept potential low yield fractures in possible communication with the school well. However, after multiple well development Page 5-3 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra events; the well made very little water with very slow recovery (weeks) after pumping and was utilized as a piezometer. A replacement of BG-01BRL was verbally approved by DEQ on November 17, 2016 (E. Rice, DEQ, to K. Witt, DEP). The replacement well, BG-01BRLR, was installed to a depth of 400 bgs by GeoEx using air hammer drilling techniques. No significant water bearing fractures (> 1.0 gpm) were encountered during borehole installation with the exception of a zone determined at 154 feet bgs. Therefore, a 10 foot pre -packed screen was set from 150 to 160 feet bgs. The remainder of the boring below the screened interval was backfilled with a high solids bentonite grout (AquaGuard®). The boring log with lithologic descriptions and well information for BG-1BRLR is included in Appendix C. Well construction information for the existing and newly monitoring wells is summarized in Table 5-3. 5.4 Groundwater Sampling One groundwater sampling event of the existing and newly installed monitoring wells associated with the impoundments and discharge canals was conducted in March 2017. Samples were collected using low -flow sampling techniques utilizing either a peristaltic pump or submersible pump per the groundwater sampling procedures presented in the CSA Work Plan (SynTerra, September 2015). Groundwater samples were submitted to the Duke Energy analytical laboratory and analyzed for CSA constituents in accordance with the Work Plan. Page 5-4 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 6.0 ASH BASIN EXTENSION IMPOUNDMENTS AND DISCHARGE CANALS CHARACTERIZATION All water and sediment samples were submitted to the Duke Energy analytical laboratory for inorganic and grain size analysis in accordance with the Work Plan. Analytical reports are presented in Appendix E and tabulated herein for easy reference. 6.1 WAB Southern Extension Impoundment and Discharge Canal Sample Results SynTerra assessed the WAB SEI water and sediment quality from July 18-21, 2016 in unison with AMEC Foster Wheeler (AMECFW). The depth of the water column was measured from each sample location using an electronic water level tape and "tagging" the bottom of the pond. The deepest part of the SEI measured approximately 30 feet of water column at CF -01 (Figure 5-2). The deepest part of the impoundment is adjacent to the filter dike and depth decreases away from the filter dike within each of the fingers. 6.1.1 SEI Wastewater Data Six shallow water samples (WF -2S, WF -4S, CF -2S, CF -4S, EF -2S and EF -4S) and six deep water samples (WF -2D, WF -4D, CF -21), CF -41), EF -21) and EF -41)) were collected (Figure 5-2). The water samples were analyzed for CSA parameters with results compared to 2L and IMAC values. Water in the extension impoundment is subject only to NPDES discharge permit requirements to the heated water discharge pond via Outfall #002 and is not considered waters of the state. In this report, analytical results are compared to North Carolina 2L or IMAC standards for informational purposes to assess potential source contribution to groundwater. The analytical results indicated arsenic and cobalt greater than 2L for deep water samples collected at CF -2, CF -04, EF -02, and WF -02. Boron concentrations were greater than 2L at all locations with the exception of the deep water sample at EF - 04 (696 pg/L). Iron and manganese concentrations were greater than 2L in deep water samples at CF -02, CF -04, EF -02, EF -04 and WF -02. Manganese is also greater than 2L in surface water samples at CF -04, and WF -02, as well as deep and surface water samples at WF -04. Thallium concentrations were greater than 2L at CF -02 SW, WF-02SW and WF-04DW. Vanadium concentrations were detected above IMAC in all water samples. Constituent concentrations in samples collected within two feet of the impoundment bottom tended to be greater than 2L and exhibited higher turbidities than the corresponding surface water sample. In most cases, constituent concentrations decreased with distance Page 6-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra from filter dike. Analytical results are summarized in Table 6-1 and the analytical reports are provided in Appendix E. 6.1.2 SEI Discharge Canal Wastewater Data Six water samples (WDC -1 through WDC -6) were collected from the discharge canal. Sample locations WDC -3 — WDC -6 were accessed using a pontoon boat following DEP-approved boat safety protocol. Sample locations WDC -1 and WDC -2 were accessed on foot and collected from the shore line. The water samples were analyzed for CSA parameters and the results compared to 2L and IMAC values. Water in the discharge canal is subject only to NPDES discharge permit requirements to the heated water discharge pond via Outfall #002 and is not considered waters of the state. Therefore, the 2L comparisons are for informational purposes to assess potential source contribution to groundwater. Analytical results indicate boron, iron, manganese, and vanadium greater than 2L and IMAC at all sample locations. In general, the constituents increased in concentration downstream from the filter dike (WDC -01) towards NPDES Outfall #2 (WDC -06). Analytical results are summarized in Table 6-1 and the analytical reports are provided in Appendix E. 6.1.3 SEI Surficial and Core Sediment Data Surficial sediment samples and cores were collected from seven locations in the SEI (EF -1, EF -3, CW -1, CF -3, CF -5, WF -1 and WF -3) using a direct push barge mounted GeoProbe with core samples collected to probe refusal. The depth to the bottom of the impoundment was recorded and the lithology of intact core samples described. Ash of variable thickness from 1— 5 feet was observed in the surficial and core sediment samples. Field verification determined the presence of CCR material at all locations; therefore, no additional laboratory confirmation was warranted. The sediment core photographs and boring logs are provided in Appendix D. The sediment samples were analyzed for CSA parameters and compared to the USEPA Regional Screening Levels (RSLs) for Soil for Protection of Groundwater. Analytical results indicate arsenic, selenium, and vanadium concentrations were in exceedance of the RSL in all sediment samples collected. Barium and lead were detected above the RSL in most samples with the exception of EF -01 and EF -03 (barium) and EF -03 and WF -03 (lead). Copper was detected above the RSL in CF -03. Analytical results are summarized in Table 6-2 and the analytical reports are provided in Appendix E. Page 6-2 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra The SPLP leaching test was used to assess if the metals present in sediment samples may leach to groundwater. Leachate samples collected from CL -02, CL - 04, CL -06, CL -07, CV -01, and CV -02 were analyzed for CSA parameters and compared to 2L and IMAC values. Cobalt, iron, manganese and vanadium leachate concentrations were greater than 2L or IMAC at all sample locations. Antimony and arsenic leachate concentrations were greater than 2L at CF -03, CF - 05, EF -01 and WF -01. The arsenic leachate concentration is also greater than 2L at CF -01. At sample location WF -01, beryllium, cadmium and selenium leachate concentrations were greater than 2L. Chromium and lead leachate concentrations were greater than 2L at CF -01 and WF -01 and thallium leachate concentrations were greater than 2L at sample locations EF -01 and WF -01. With the exception of antimony, arsenic, selenium and thallium in the sediment samples, the SPLP analysis for sediment samples from the SEI are consistent with SPLP analysis of soil, including background locations, presented in the CSA. The SPLP results are summarized in Table 6-3. Laboratory analytical reports are provided in Appendix E. 6.1.4 SEI Discharge Canal Sediment and Core Sediment Data Six sediment samples (WDC -1 through WDC -6) were collected using a Ponar Dredge. Sample locations WDC -3 through WDC -6 were accessed using a pontoon boat. Sample locations WDC -1 and WDC -2 were accessed on foot and collected from the shore line. Sediment core samples were manually collected with the clear acetate sleeves at WDC -1, WDC -2, WDC -4, WDC -5 and WDC -6. Field observations indicated the presence of coal ash in the samples ranging from less than 1 foot to 1.5 feet in thickness. Field verification determined the presence of CCR material at all locations; therefore, no additional laboratory confirmation was warranted. The sediment core photographs and boring logs are provided in Appendix D. The sediment samples were analyzed for CSA parameters and compared to the USEPA RSLs for Soil for Protection of Groundwater. Analytical results indicate arsenic, selenium, and vanadium concentrations were in exceedance of the RSL in all sediment samples collected. Barium was detected above the RSL in most samples with the exception of WDC --03. Antimony was detected above the RSL in WDC -04. Copper was detected above the RSL in WDC -04, WDC -05 and WDC -06. Mercury was above the RSL in WDC -05 and WDC -06. As with the water samples, the constituents increased in concentration downstream from the filter dike (WDC -01) towards NPDES Outfall #002 (WDC -06). Analytical results Page 6-3 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra are summarized in Table 6-2 and the analytical reports are provided in Appendix E. 6.1.5 SEI Groundwater Data The monitoring well, MW-26BR, was installed near the eastern side of the eastern finger of the SEI to support existing wells, CW -04 and MW-04BR, to evaluate groundwater quality in the upper bedrock. Groundwater samples were collected in one event during the first quarter of 2017 and analyzed for CSA parameters. Analytical results are compared to 2L and IMAC values as well as the provisional background concentrations. Analytical results indicate iron and manganese greater than 2L in MW-26BR. However, the detected concentrations are consistent with background concentrations. No boron was detected above the method detection limit (50 µg/L) in the impoundment wells. An isoconcentration map representing the most recent analytical data for boron is provided in Figure 6-1. The most recent analytical data is summarized in Table 6-4 and the laboratory analytical reports are included in Appendix E. 6.1.6 SEI Discharge Canal Groundwater Data The monitoring wells MW-31BR, MW-32BR and MW-33BR were installed to support existing wells, MW-07BR, MW-08BR, and MW -12, to evaluate groundwater quality in the bedrock along the western discharge canal. Groundwater samples were collected in one event during the first quarter of 2017 and analyzed for CSA parameters. Analytical results are compared to 2L and IMAC values as well as the provisional background concentrations. Analytical results indicate that constituents were detected above the 2L or IMAC including chromium (16.2 µg/L (MW-33BR)); manganese (575 µg/L (MW-31BR), 76 pg/L (MW-32BR), and 100 µg/L (MW-33BR)); sulfate (310 µg/L (MW-32BR)); total dissolved solids (660 µg/L (MW-32BR)); and vanadium (2.28 µg/L (MW- 31BR), 0.876 µg/L (MW-32BR) and 1.3 pg/L (MW-33BR)). Boron was not detected in any of the groundwater samples above the method detection limit (50 pg/L). An isoconcentration map representing the most recent analytical data for boron is provided in Figure 6-1. The detected concentrations are consistent with background concentrations with the exception of sulfate and total dissolved solids in MW-32BR, though the data reflects one sampling event. The most recent analytical data is summarized in Table 6-4 and the laboratory analytical reports are included in Appendix E. Page 6-4 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 6.2 EAB Eastern Extension Impoundment and Discharge Canal Sample Results SynTerra was retained to evaluate the water, sediment and groundwater quality conditions associated with the EEI. SynTerra conducted water and sediment sampling of the EEI on April 26-27, 2016 and installed and sampled groundwater monitoring wells in June 2016. Results of the EEI investigation were presented in the CSA Supplement 1 report (SynTerra, August 1, 2016). 6.2.1 EEI Wastewater Data A total of four shallow water samples (CL -2S, CL -5S, CV -2 and CL -7) and two deep water samples (CL -2 and CL -5) were collected (Figure 5-3). Sample locations were accessed using an inflatable boat. The shallow water samples were collected from the top foot of the water column. Deep water samples were collected using a peristaltic pump with weighted tubing approximately two feet from the bottom of the water column. The sample depth, sample location, and field parameters (pH, conductivity, dissolved oxygen, temperature, and turbidity) were recorded. The water samples were analyzed for CSA parameters and results compared to 2L and IMAC values. Water in the extension impoundment is part of the ash basin and is not considered waters of the state. In this report, analytical results are compared to North Carolina 2L or IMAC standards for informational purposes to assess potential source contribution to groundwater. The analytical results indicated boron, manganese, and vanadium greater than 2L or IMAC in all samples. Iron was detected greater than 2L in CL -02 and CL - 05. Analytical results are summarized in Table 6-5 and the analytical reports are provided in Appendix E. 6.2.2 EEI Discharge Canal Wastewater Data Five water samples (EDC -1- EDC -5) were collected from the eastern discharge canal. EDC -1 was accessed using a pontoon boat. All other sample locations were accessed on foot. Grab water samples from the discharge canal were collected into sample bottleware provided by the analytical laboratory. The water samples were analyzed for CSA parameters and results compared to 2L and IMAC values. Water in the discharge canal is part of the ash basin and is not considered waters of the state. In this report, analytical results are compared to North Carolina 2L or IMAC standards for informational purposes to assess potential source contribution to groundwater. Page 6-5 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra The analytical results indicated boron, manganese (with the exception of EDC - 02), and vanadium are greater than 2L or IMAC in all samples. Cobalt was detected in EDC -05 greater than 2L at 1.53 µg/L. Iron was detected greater than 2L in EDC -01, EDC -04 and EDC -05. There appears to be no apparent trend regarding constituent concentration from the confluence of the discharge canal with the impoundment (EDC -01) to the discharge point near the intake canal (EDC -05). Though, boron concentrations appear greater near the impoundment (EDC -01). Analytical results are summarized in Table 6-5 and the analytical reports are provided in Appendix E. 6.2.3 EEI Surficial and Core Sediment Data Four shallow sediment samples (NL -8, SL -8, CV -2, and NL -4) and five deeper sediment cores (CL -2, CL -4, CL -6, CV -1, and CL -7) were collected. Shallow sediment was collected from the top six inches of the sediment using a Ponar dredge. Intact core samples were collected using the direct push barge mounted GeoProbe with core samples collected to probe refusal. Sediment samples were collected after the shallow water samples to minimize potential sediment disturbance. The depth to the bottom of the impoundment was recorded and the lithology of intact core samples described. Ash thickness from <1 to 20 feet was observed within the impoundment, which was greatest near the separator dike. Field verification determined the presence of CCR material at all locations; therefore, no additional laboratory confirmation was warranted. The sediment boring logs are provided in Appendix D. The sediment samples were analyzed for CSA parameters and compared to the USEPA RSLs for Soil for Protection of Groundwater. Analytical results indicate arsenic, selenium, and vanadium concentrations were greater than the RSL in all sediment samples collected with the exception of CL -02, CL -06 (arsenic and selenium) and CV -01. Barium was detected greater than the RSL in CL -06, CL - 07, and NL -04. Analytical results are summarized in Table 6-6 and the analytical reports are provided in Appendix E. The SPLP leaching test was used to assess if the metals present in sediment samples may leach to groundwater. For the shallow sediment samples, cobalt, manganese and vanadium were detected greater than the 2L or IMAC in the leachate. In the deep sediment samples, antimony, arsenic, chromium, cobalt, iron, manganese, thallium and vanadium were noted higher than the 2L or IMAC in the leachate. With the exception of antimony and thallium in the deep Page 6-6 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra sediment samples, the SPLP analysis for sediment samples from the EEI are consistent with SPLP analysis of soil, including background locations, presented in the CSA. The SPLP analytical results are summarized in Table 6-7 and the laboratory analytical reports are provided in Appendix E. 6.2.4 EEI Discharge Canal Sediment and Core Sediment Data Six locations (EDC -0 through EDC -05) were slated for sediment sampling along the discharge canal. Of the six locations, four sediment samples (EDC -1, EDC -2, EDC -3, and EDC -5) were collected from the discharge canal using a clam shell sampler. A sample was not collected from EDC -4 location due to no sediment present in the concrete channel within 100 feet upstream and downstream of the location. EDC -0 and EDC -1 were accessed using a pontoon boat while all other sample locations were accessed on foot. An ash and sediment profile sample was collected from the EDC -0 location which is located in a pool at the mouth of the EDC. The pool is separated from the SEI by reeds and other organic material. Several attempts for sample collection were made at the EDC -0 location with a sample EDC -00 collected for sediment profiling. SynTerra described the sample core and determined the presence of ash of approximately 1 foot in thickness in the EDC -00 sample. Ash thickness was determined from <1 foot to 1 feet within the discharge canal, which was greatest near the confluence of the impoundment and the discharge canal. Field verification determined the presence of CCR material at all locations; therefore, no additional laboratory confirmation was warranted. The sediment core photographs and a boring log for EDC -00 are provided in Appendix D. The sediment samples were analyzed for CSA parameters and compared and compared to the USEPA RSLs for Soil for Protection of Groundwater. Analytical results indicate antimony, arsenic, barium, copper (with the exception of EDC - 05), selenium (with the exception of EDC -03), and vanadium concentrations were greater than the RSL in all sediment samples collected. Analytical results are summarized in Table 6-6 and the analytical reports are provided in Appendix E. 6.2.5 EEI Groundwater Data Three groundwater monitoring wells, MW-23BR, MW-24BR and MW-25BR, were installed around the EEI impoundment to support existing wells, MW-17BR and MW-20BRL to evaluate groundwater conditions in the upper bedrock (Figure 5- 3). Groundwater samples were initially collected from the EEI impoundment wells on June 16-17, 2016 for CSA parameters and compared to 2L and IMAC values. Analytical results indicated that several constituents were detected Page 6-7 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra greater than the 2L or IMAC in one or more of the wells including antimony, total chromium, iron, manganese, TDS, and vanadium. With the exception total chromium and TDS in MW-25BR, none of the detected constituents were above the provisional background concentrations. Boron was not detected in any of the groundwater samples suggesting the ash present in the EEI has not impacted the groundwater in the upper bedrock aquifer. Analytical summary tables and laboratory analytical reports were provided in the CSA Supplement 1 report. Groundwater samples were collected in a second sample event from the EEI impoundment wells during the first quarter of 2017 and analyzed for CSA parameters with comparison to 2L and IMAC values. Analytical results indicated that several constituents were detected greater than the 2L or IMAC in one or more of the wells including total chromium, iron, manganese, TDS, and vanadium. With the exception of TDS in MW-25BR, none of the detected constituents were above the provisional background concentrations. Boron was not detected in any of the groundwater samples which continue to support that ash present in the EEI has not impacted the groundwater in the upper bedrock aquifer. An isoconcentration map representing the most recent analytical data for boron is provided in Figure 6-1. The most recent analytical data is summarized in Table 6-8 and the laboratory analytical reports are included in Appendix E. 6.2.6 EEI Discharge Canal Groundwater Data The monitoring wells MW-27BR through MW-30BR were installed to evaluate groundwater quality in the bedrock along the EEI discharge canal. Groundwater samples were collected during the first quarter of 2017 and analyzed for CSA parameters. Analytical results are compared to 2L and IMAC values as well as the provisional background concentrations. Analytical results indicated that several constituents were detected greater than the 2L or IMAC in one or more of the wells including iron (MW-30BR), manganese (MW-27BR, MW-28BR and MW-30BR), TDS (MW-27BR and MW- 30BR), and vanadium (all wells). None of the detected constituents were above the provisional background concentrations. Boron was not detected in any of the groundwater samples. An isoconcentration map representing the most recent analytical data for boron is provided in Figure 6-1. Analytical data demonstrates the ash present in the discharge canal has not impacted groundwater in the upper bedrock aquifer. The most recent analytical data is summarized in Table 6-8 and the laboratory analytical reports are included in Appendix E. Page 6-8 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 7.0 GROUNDWATER MODEL AND GEOCHEMICAL MODEL Groundwater modeling and geochemical modeling of the Roxboro Site have been conducted to predict the fate of coal ash constituents in groundwater and changes in groundwater geochemistry under differing remediation scenarios. Integration of impoundment and discharge canal assessment data into future groundwater modeling and geochemical modeling is discussed in the following subsections. 7.1 Groundwater Model Future updates to the Site's groundwater flow and transport model will account for the newly installed impoundment and discharge canal assessment wells and associated groundwater data. The findings from the initial assessment data appear similar to projections provided in previous models presented in the CAP Part 1 and CAP Part 2. 7.2 Geochemical Model Future updates to the Site's geochemical model will include groundwater data collected from the newly installed impoundment and discharge canal assessment wells. No significant differences in pH/ORP from the assessment data were determined to anticipate changes to the outcome of the geochemical model. Page 7-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 8.0 UPDATED SITE CONCEPTUAL MODEL Hydrogeologic and geochemical site conceptual models (SCMs) were developed for the coal ash basins and presented in Section 6.0 of the CSA Report (SynTerra, September 2015) and revised, based on fate and transport modeling, in the CAP Part 1 (SynTerra, December 2015). A refined SCM was presented in the CAP Part 2 (SynTerra, February 2016) based on the updated fate and transport and geochemical modeling. Additional site specific geologic, hydrogeologic and geochemical information was presented in the CSA Supplement 1 (SynTerra, August 2016). The SCM will continue to be refined as additional site-specific information is obtained from the impoundment and discharge canal assessment process. Water level measurements for all CSA wells were collected during a 24-hour period on April 10, 2017 for comparison to previous measurements collected during the CSA. The water level data are presented in Table 8-1. Individual water level maps for the saprolite and the transition zones were not made due to the limited occurrence of saturated conditions in those units. A generalized water level map for the bedrock aquifer, including the saprolite and transition zone hydrogeologic units, is included on Figure 8-1. No significant changes in water levels or groundwater flow directions were noted in April 2017 water level map as compared to the previous maps presented in the CAP Part 2 report (SynTerra, February 29, 2016) and the CSA Supplement 1 report (SynTerra, August 1, 2016). Downward gradients were noted in most locations between transition zone and bedrock wells and between upper and lower bedrock wells. The vertical gradient magnitude and direction is similar to vertical gradient presented in the CSA report (September 2015). Revised conceptual geological cross-sections across the East and West Ash Basins were developed incorporating lithological information obtained from the impoundment and discharge canal assessment activities, data compiled from the NCDEQ water supply well sampling events, and groundwater elevations from April 2017. The cross-sectional transect lines A -A' and B -B' are indicated on Figure 8-2. Section A -A' show conditions in the West Ash Basin in relation to the upgradient area to the south and the downgradient area to the north (WAB main dam and Hyco Lake) (Figure 8-3). Section B -B' illustrates conditions across the East Ash Basin, lined landfill and the extension impoundment in relation to the upgradient areas, including residential properties, to the south and downgradient areas to the north, including the Roxboro plant and intake canal (Figure 8-4). Page 8-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 9.0 CONCLUSIONS AND RECOMMENDATIONS Based on the findings of the extension impoundment and discharge canal assessment activities, the following recommendations and observations are offered: 167 Additional monitoring of the impoundment and discharge canal wells is recommended to confirm the initial constituent concentrations. 07 Future groundwater flow and transport modeling and geochemical modeling will need to incorporate additional data to evaluate the impoundments and discharge canals. ,67 No substantive changes to previous site conceptual model or previously predicted migrations of constituents from the ash basins were observed. H Extend the compliance boundary to include the impoundments and related discharge canals per the 'Proposed Waste and Compliance Boundary" submitted by Duke Energy on August 19, 2016 in response to the Division of Water Resources July 8, 2016 request. Page 9-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS) \ DC Assessment Report \ Final Roxboro Discharge Canal Assess Rpt.docx Ash Basin Extension Impoundments and Discharge Canals Assessment Report May 2017 Roxboro Steam Electric Plant — Semora, NC SynTerra 10.0 REFERENCES AMEC Foster Wheeler, Duke Energy Coal Combustion Residuals Management Program, Roxboro Steam Station, June 16, 2015. Duke Energy, 2014; http://www.duke-energy.com/pdfs/duke-energy-ash-metrics.pdf (Updated June 23, 2016) SynTerra. Drinking Water Well and Receptor Survey for Roxboro Steam Electric Plant, NPDES Permit# NC0038377. September 2014. SynTerra. Supplement to Drinking Water Well and Receptor Survey for Roxboro Steam Electric Plant, NPDES Permit# NC0038377. November 2014. SynTerra. Proposed Groundwater Assessment Work Plan for Roxboro Steam Electric Plant (Revision 1). December 30, 2014. SynTerra. Comprehensive Site Assessment Report - Roxboro Steam Electric Plant. September 2, 2015. SynTerra. Corrective Action Plan Part 1 - Roxboro Steam Electric Plant. December 1, 2015 SynTerra, Corrective Action Plan Part 2 — Roxboro Steam Electric Plant. February 29, 2016 SynTerra, Comprehensive Site Assessment Supplement 1— Roxboro Steam Electric Plant. August 1, 2016 Page 10-1 P:\Duke Energy Progress.1026\107. Roxboro Ash Basin GW Assessment Plan\33.Discharge Canal Assessment (EHS)\DC Assessment Report \Final Roxboro Discharge Canal Assess Rpt.docx