The URL can be used to link to this page

Home My WebLink AboutRevised PM 2015_12_18 Summary Information on Ash Basins for NCDEQExecutive Summary Duke Energy Carolinas, LLC and Duke Energy Progress, LLC (collectively, "Duke Energy") have met and will continue to meet all requirements of the North Carolina Coal Ash Management Act of 2014 ("CAMA") including provisions for use, permitting, monitoring, assessment, and closure planning at coal ash surface impoundments. With respect to groundwater, Duke Energy has submitted Groundwater Assessment Reports/Comprehensive Site Assessments ("GAR/CSAs")' and Part 1 Groundwater Corrective Action Plans ("CAPs") that contain the elements specified by CAMA. This information was provided, in part, to support the development of proposed classifications by the Department of Environmental Quality (the "Department" or "DEQ"). Duke Energy has also agreed to provide additional information that can be used by the Department to further evaluate the proposed classifications in the future as it receives and responds to public comment. Information submitted to the Department shows that none of Duke Energy's ash basin sites, with the exception of Sutton, pose an imminent hazard to human health or the environment. Modeling performed for CAP Part 1 submittals illustrates that ash -related impacts are at steady state, meaning they will not change substantially in the future, even without corrective action. A steady state is consistent with ash management units that have been in operation for decades, in some cases more than fifty years. Published scientific literature on hydrogeology in North Carolina, site-specific monitoring collected as required by National Pollutant Discharge Elimination System ("NPDES") permits, and the recent GAR/CSA data confirm with increasing precision that ash constituents are generally flowing from ash impoundments away from upgradient receptors and toward the nearest river or lake. Data show little to no impact in bedrock wells, which is consistent with the fact that these constituents have a density similar to water and do not naturally sink into deeper layers. Data and analysis suggest that overall site groundwater flow direction is unaffected by the presence of fractured rock, local effects from mounding of water by ash basins, or the collective effect of pumping by off-site wells. Corrective action assessment and planning will continue, with additional well installation, monitoring, and modeling to further increase the resolution with which the sites are characterized. These data will be shared with DEQ as Duke Energy works aggressively to clean up all sites using the best science and engineering, while continuing to meet CAMA provisions and requirements of the U.S. Environmental Protection Agency's Coal Combustion Residuals Rule. Although the additional assessment may be useful to the Department in the separate process of developing CAMA risk classifications for the impoundments, decisions regarding groundwater corrective action and basin closure will be driven by different considerations. For example, if an impacted receptor were identified or significantly threatened, the most expeditious corrective action would be drinking water replacement along with targeted groundwater remediation, not excavation, which would take longer and create ancillary negative impacts to the surrounding community. As a result, regardless of the additional work to be performed for corrective action planning, data and information already submitted create a substantial administrative record on which the Department can develop proposed CAMA classifications in the near term. CAMA uses the term "Groundwater Assessment Report" (E.g., N.C. Gen. Stat. § 130A -309-211(a)(4)), but the reports were submitted under the more conventional title of "Comprehensive Site Assessment." Contents ExecutiveSummary.....................................................................................................................i Section1 - Introduction.............................................................................................................. 1 Section 2 — CAMA Requirements............................................................................................... 1 Groundwater Assessment and Corrective Action.................................................................... 2 Prioritization............................................................................................................................ 2 Section 3 — Groundwater Assessments..................................................................................... 3 Allen....................................................................................................................................... 3 Asheville................................................................................................................................. 4 BelewsCreek......................................................................................................................... 5 Buck....................................................................................................................................... 6 CapeFear.............................................................................................................................. 7 Cliffside.................................................................................................................................. 8 DanRiver............................................................................................................................... 9 HFLee..................................................................................................................................10 Marshall.................................................................................................................................11 Mayo.....................................................................................................................................12 Riverbend..............................................................................................................................13 Roxboro.................................................................................................................................14 Sutton....................................................................................................................................14 Weatherspoon.......................................................................................................................15 Section 4 — Status of Ongoing Work.........................................................................................16 Supplemental Investigation, Monitoring and Analysis............................................................16 Corrective Action Plan Part 2s...............................................................................................17 Section 5 —Additional Data.......................................................................................................18 Section 6 — Responses to Comments.......................................................................................18 Department Comment: .......................................................................................................... 18 DukeEnergy Response: ........................................................................................................ 18 DepartmentComment: .......................................................................................................... 19 Duke Energy Response: ........................................................................................................ 19 DepartmentComment: .......................................................................................................... 20 Duke Energy Response: ........................................................................................................ 21 DepartmentComment...........................................................................................................21 Duke Energy Response: ........................................................................................................ 21 Section 7 — Review and Commentary: Groundwater Assessment and Corrective Action ..........21 Mounding..............................................................................................................................22 Deepfractures.......................................................................................................................22 Pumping................................................................................................................................23 Depth of GAR/CSA wells versus receptor wells.....................................................................23 Changes in Geochemistry .....................................................................................................23 SaturatedAsh........................................................................................................................24 ConstituentModeling.............................................................................................................24 Section 8 - Responses to Comments from Others....................................................................25 Section 9 — Evaluation of DEQ Drinking Water Data.................................................................25 Section 10 - Closure Alternatives..............................................................................................27 Conclusion................................................................................................................................28 Appendices 1. Presentation 2. CAMA Requirements 3. Executive Summaries 4. Ongoing Work 4.1 Additional Well Locations 4.2 Sample CAP Part 1 TOCs 4.3 Sample CAP Part 2 TOCs 5. Additional Data 6. Response to DEQ Comments 6.1 Background Calculations 6.2 Model Tables 7. Responses to Other Comments 7.1 Drinking Water Well Model Runs 8. Responses to SELC Comments 8.1 HDR response to Allen, Buck, and Marshall comments 8.2 Synterra response to Mayo comments 8.3 Synterra response to Roxboro comments 9. Bradley Report Section 1 - Introduction Since the enactment of CAMA on September 20, 2014, Duke Energy and the Department have undertaken a variety of initiatives to comply with CAMA's requirements for use, permitting, monitoring, assessment, and closure planning at coal ash surface impoundments. A significant portion of the work has been directed at complying with CAMA's requirements related to groundwater assessment and corrective action, including: timely submission by Duke Energy of proposed Groundwater Assessment Plans ("GAPs"); review and approval of GAPs by the Department; timely submission by Duke Energy of GAR/CSAs; review of GAR/CSAs and requests for additional information by the Department; timely submission by Duke Energy of Part 1 CAPs; identification by Duke Energy of downgradient private water supply wells within a half mile of coal ash surface impoundment compliance boundaries, followed by sampled coordinated by the department ;2 and voluntary proactive provision of alternate water supplies to private water supply well owners whose wells exceed standards identified by DEQ and the Department of Health and Human Services. Additionally, Duke Energy is scheduled to submit Part 2 CAPs over the next few months, and the Department is scheduled to develop proposed classifications prioritizing coal ash surface impoundments for closure by year-end. This document, with its attachments, provides a summary of the results of these initiatives. Some of the information has already been provided to the Department in prior submissions, while some of the information is new. In some cases, Duke Energy has accelerated the completion of analyses originally intended for inclusion in future submittals. Each section of this document contains a summary of the more detailed contents of the longer attachments. At DEQ's request, Duke Energy has provided summary information regarding the groundwater investigations at the various sites as well as an analysis of available background information for offsite wells sampled by DEQ. Please find a copy of our December 14, 2015 presentation to DEQ in Appendix 1. Section 2 — CAMA Requirements Working under the oversight of the Department, Duke Energy has complied with CAMA's requirements to generate and submit GAPs, GAR/CSAs, and CAPs. At the Department's direction, Duke Energy has gone beyond the requirements of CAMA in sampling private water supply wells. As explained in Appendix 2, although the Department has requested additional 2 Although not required by CAMA, upgradient private water supply wells were also sampled. information, the identification of additional information is consistent with CAMA's iterative process for the collection of information and does not weigh against a conclusion that Duke Energy has met its legal obligations. Further, although more information may provide additional precision to the assessments, there is no basis in theory or data for a prediction that additional data will materially change the results of the analysis. The information submitted to date, and information that will be submitted in the near future, is technically sound. There is no legal or technical reason that the Department cannot rely on this information in carrying out its obligation to prioritize coal ash impoundments. Groundwater Assessment and Corrective Action The groundwater assessment and corrective action provisions in North Carolina General Statutes § 130A-309.212 require Duke Energy to submit and implement GAPs and to generate resulting GAR/CSAs. They do not require that the GAR/CSAs conclusively describe any specific aspect of groundwater dynamics at a site, other than identifying exceedances of groundwater standards. In fact, the provisions anticipate that data gaps identified in GAR/CSAs will be addressed in CAPs and other later CAMA stages. CAMA specifically assigns the Department checkpoints to review and approve Duke Energy submissions: review and approval of GAPs and review and approval of CAPs. In each case, the Department has two tasks: (1) determine if the GAP or CAP meets the requirements of the section by containing the specified minimum information, and (2) determine if the GAP or CAP is sufficient to protect public health, safety, and welfare; the environment; and natural resources. The Department has already determined on the record that GARs satisfy both. Complete CAPs are not yet due under the schedule set by the Department pursuant to CAMA, so they have not yet been submitted and are not ripe for such a determination. A finding by the Department that additional information would be useful is not the equivalent of a finding that the GARs or CAPs are deficient or did not meet the requirements of CAMA by providing the specified elements. Further, any such determination by the Department is subject to normal legal standards that apply to agency decision making. As the Department has noted, it would be arbitrary and capricious to hold Duke Energy to a different standard than other regulated parties when evaluating the amount of data submitted Prioritization With respect to prioritization, Duke Energy is committed to meeting the Department's expectations by providing additional data, fully leveraging the time provided CAMA's iterative process to ensure final classifications reflect the best science and engineering. Nonetheless, there is already a significant amount of technically sound and legally valid evidence regarding the factors that CAMA requires the Department to consider. Both CAMA and general administrative law indicate that the Department's prioritization decisions should be based on information in the administrative record, and the Department's decision must be based on substantial evidence in the record. Additional information may bolster the record in the future, but the record is already sufficient to support development of proposed classifications. 2 Section 3 — Groundwater Assessments In accordance with N.C. Gen. Stat. § 130A -309.211(a), Duke Energy timely submitted proposed GAPs for all fourteen coal-fired plants. As required by that section, the proposed GAPs provided for all of the following: (a) a description of all receptors and significant exposure pathways; (b) an assessment of the horizontal and vertical extent of soil and groundwater contamination for all contaminants confirmed to be present in groundwater in exceedance of groundwater quality standards; (c) a description of all significant factors affecting movement and transport of contaminants; (d) a description of the geological and hydrogeological features influencing the chemical and physical character of the contaminants; and (e) schedule for continued groundwater monitoring. The Department provided comments on those proposed GAPs, and Duke Energy submitted revised GAPs on December 30, 2014, which reflected those comments. The revised proposed GAPs were conditionally approved by DEQ in accordance with N.C. Gen. Stat. § 130A -309.211(a)(2), indicating that the work plans met the requirements of CAMA, except for specifically noted exceptions. Duke Energy subsequently executed those approved GAPs with frequent consultation with DEQ, including communications to address the exceptions and to ensure strict compliance with CAMA. Based on the accumulation and analysis of the data generated and analyzed as required in the approved GAPs, Duke Energy timely submitted GAR/CSAs to DEQ in accordance with N.C. Gen. Stat. § 130A -309.211(a)(4) on several dates from August 4, 2015 to September 9, 2015. The Executive Summary from each of the fourteen CSAs is included in Appendix 3. For convenience, highlights of those executive summaries are included below. Allen Allen Steam Station is owned and operated by Duke Energy Carolinas and is located near the town of Belmont, in Gaston County, North Carolina. The Allen ash basin system consists of an active ash basin and an inactive ash basin. Two unlined dry ash storage areas, two unlined structural fill units, and a double -lined dry ash landfill are located within the footprint of the inactive ash basin. Voluntary groundwater monitoring for Allen's ash basin system began in May 2004 and continued until November 2010. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. Duke Energy submitted a GAR/CSA for Allen in August 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the active ash basin and inactive ash basin. At Allen, groundwater in the shallow, deep, and bedrock flow layers beneath the ash basin system generally flows horizontally, to the east toward the Catawba River, except that groundwater beneath a portion of the inactive ash basin which flows north and northeast toward Duke Energy property and the station's discharge canal. This flow direction is away from the nearest public and private water supply wells. The GAR/CSA states that the direction of migration of coal ash -related contaminants in groundwater is east toward the Catawba River. 3 The approximate horizontal extent of groundwater impacts is limited to beneath and immediately downgradient of the ash basin system to the east and north, within the Duke Energy property boundary. The approximate vertical extent of groundwater impacts is generally limited to the shallow and deep flow layers. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The horizontal extent of soil contamination is limited to the area beneath the ash basin. The vertical extent of soil contamination was determined to be generally limited to the uppermost soil sample collected beneath the ash basin. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, soil and groundwater impacts are present beneath and downgradient of the ash basin. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are in the process of being addressed to better understand groundwater quality and flow characteristics at the site and to the west of the site near the of public and private drinking water supply wells, but, based on known site characteristics, additional data is not anticipated to materially change current conclusions. Allen's CAP Part 1 was submitted in November 2015. Proposed provisional background concentrations ("PPBCs") are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Asheville Asheville Steam Electric Plant is owned and operated by Duke Energy Progress and is located near Asheville, in Buncombe County, North Carolina. Two ash basins, designated the 1964 ash basin and 1982 ash basin, are situated directly southwest of the Plant and bordered to the southwest by steep topographic relief and 1-26. The 1982 ash basin is no longer in use. An area of constructed wetlands and the current ash dewatering rim ditch system are built within the boundary of the 1964 ash basin. Monitoring of Asheville Plant compliance boundary wells began in November 2010 and is conducted triennially in accordance with the NPDES permit conditions. Groundwater at the Asheville Plant occurs in surficial, transition zone, and bedrock flow regimes. Hydraulic data indicate groundwater flow generally follows topography to the west towards the French Broad River. The GAR/CSA determined that the direction of the migration of contaminants related to coal ash is toward the French Broad River. The GAR/CSA determined the vertical and horizontal extent of soil contamination at the Site. Constituents attributable to the source area, such as arsenic, detected above the protection of groundwater standard are generally found within the ash basin foot print and at a depth directly beneath the ash/soil interface. Aluminum, cobalt, iron, manganese, and selenium are detected beyond the ash basin footprint in isolated areas. 59 Findings from the Comprehensive Site Assessment at Asheville Steam Electric Plant lead to the conclusions that there is no imminent hazard to human health or the environment due to soil or groundwater impacts at the site. The approximate horizontal extent of groundwater impacts is limited to beneath the ash basin and downgradient of the ash basin to the west. The horizontal extent of migration is controlled by the French Broad River to the west, which acts as a major groundwater to surface water discharge zone. Groundwater impacts have been identified in the surficial, transition zone, and bedrock flow systems. Seep data indicate that groundwater discharges along the French Broad River floodplain, consistent with the current site conceptual model. The aerial extent of groundwater impact is represented by boron, the most mobile constituent commonly associated with potential coal ash contamination, and depicted in the Executive Summary Figure 1. Additional work is currently being performed at the Asheville Site to address data gaps discussed during a meeting with the DEQ Asheville Regional Office conducted on October 19, 2015. Two additional wells are being installed to provide a more precise understanding of geochemical conditions within the bedrock flow system beneath the ash basin and at a background location. Successful redevelopment of a background transition zone well with elevated pH will allow for an additional transition zone background well to be added to the data set. Impacts to private water supply wells are being addressed by installation of a water line along Bear Leah Trail, which is nearing completion. Prior to abandoning these private supply wells, a full suite of geophysical logs will be run to provide a detailed view of the nature of groundwater flow in the fractured bedrock flow system to the south of the Plant. Resampling of a private supply well has been scheduled to confirm initial results. Belews Creek Belews Creek Steam Station is owned and operated by Duke Energy and is located near the town of Walnut Cove, in Stokes County, North Carolina. The Belews Creek ash basin consists of an active ash basin and an inactive ash basin. Two unlined dry ash storage areas, two unlined structural fill units, and a double -lined dry ash landfill are located within the footprint of the inactive ash basin. Voluntary groundwater monitoring for Allen's ash basin began in May 2004 and continued until November 2010. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. Duke Energy submitted the GAR/CSA for Belews Creek in September 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the active ash basin and inactive ash basin. At Belews Creek, groundwater and in the shallow, deep, and bedrock flow layers beneath the ash basin flows horizontally to the north and northwest toward the Dan River as does the migration of coal ash related contaminants. This flow direction is away from the nearest public and private water supply wells. The approximate horizontal extent of groundwater impacts is limited to beneath the ash basin and immediately downgradient of the ash basin to the north 61 and northwest. The approximate vertical extent of groundwater impacts is generally limited to the shallow and deep flow layers. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The horizontal extent of soil contamination is limited to the area beneath the ash basin. The vertical extent of soil contamination was determined to be generally limited to the uppermost soil sample collected beneath the ash basin. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, soil and groundwater impacts are present beneath and downgradient of the ash basin. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site and to the west of the site. The CAP Part 1 was submitted in November 2015. PPBCs are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Buck Buck Steam Station is owned and formerly operated by Duke Energy and is located near the town of Salisbury, in Rowan County, North Carolina. The Buck ash basin system consists of an ash basin with three cells that no longer receives coal ash from the decommissioned steam plant. A dry ash storage area also exists on site within the footprint of the ash basin system. Voluntary groundwater monitoring for Buck's ash basin system began in November 2006 and continued until May 2010. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. As required by CAMA, Duke Energy submitted a GAR/CSA in August 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the ash basin. At Buck, groundwater in the shallow, deep, and bedrock flow layers beneath the ash basin predominantly flows in the north direction toward the Yadkin River, with a component of flow to the west of Cell 1. Additionally, there is localized flow in an area east of the surface water in cell 2 that requires further evaluation (between Cells 2 and 3). These flow directions are away from the nearest public and private water supply wells. The GAR/CSA found that the direction of migration of coal ash -related contaminants in groundwater is north toward the Yadkin River. The approximate horizontal extent of groundwater impacts is limited to beneath the ash basin and ash storage area and immediately downgradient of the ash basin and ash storage area to the n north, within the Duke Energy property boundary. The approximate vertical extent of groundwater impacts includes the shallow, deep, and bedrock flow layers. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The Constituent of Interest ("COI") concentrations observed in the soil from the various locations within the Buck site generally bracket the concentrations observed in soil samples from the background locations or within reasonable proximity of the bracketed background concentrations. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, groundwater impacts are present beneath and downgradient of the ash basin. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site. The CAP Part 1 was submitted in November 2015 to support the DEQ's risk ranking classification for the Buck's ash basin system. PPBCs are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Cape Fear The Cape Fear Steam Electric Plant is owned and formerly operated by Duke Energy Progress and is located on approximately 900 acres in Chatham County at 500 CP&L Road, Moncure, North Carolina. The Cape Fear Plant began producing power in 1923 and was retired in 2012. The Plant is currently being decommissioned. CCR produced from the combustion of coal were sluiced to five ash basins, referenced using the approximate year of construction: 1956, 1963, 1970, 1978, and 1985. The ash basins were developed near original ground surface with excavation of Site soils for construction of the perimeter dikes. Collectively the five ash basins encompass approximately 173 acres and contain approximately 5,670,000 tons of CCR. Duke Energy performed voluntary groundwater monitoring around the 1985 ash basin from March 2007 until April 2010. In 2010, Duke Energy installed a set of background wells and compliance boundary wells around each ash basin. Groundwater monitoring, as part of NPDES permit conditions, began in 2010 and continues three times a year. Geology at the Site consists predominantly of alluvium (clays grading downward to sands) also referred to as the surficial hydrostratigraphic unit over sedimentary rocks (mudstone and sandstone) referred to as the bedrock hydrostratigraphic unit. Groundwater flow direction within each hydrostratigraphic unit generally mimics surface topography and migrates toward surface water discharge features including Shaddox Creek on the north, an unnamed tributary to the Cape Fear River referred to as `Branch A' on the east, the cooling water effluent channel and an unnamed tributary on the south and central portions of the Site, and the Cape Fear River on the west. Surface water in the area drains to the Cape Fear River. 7 Several constituents detected in groundwater are ubiquitous and/or occur naturally in the vicinity of the Site at concentrations greater than applicable regulatory values. Hydrogeologic and geochemical data collected as part of the GAR/CSA and CAP Part 1 indicate that groundwater affected by the infiltration of ash pore water from the ash basins has not affected groundwater quality beyond the Site property boundary except for an area southwest of the 1985 ash basin were affected groundwater has migrated across a railroad right of way, currently owned by Norfolk Southern Corporation. The distribution of affected groundwater is best characterized by the presence of boron and sulfate. The boron plume is depicted in the Executive Summary Figure 1. TDS, thallium and other metals generally occur at elevated concentrations in smaller areas within the zone of elevated boron concentrations. Downward vertical migration of constituents is restricted due to the high clay and silt content of the shallow surficial deposits and fine-grained bedrock material that restricts further downward migration of constituents. Constituents related to the ash basin have not been detected above regulatory values in private supply wells near the Site or in the Cape Fear River downstream of the Site. Cliffside Cliffside Steam Station ("CSS") is owned and operated by Duke Energy and is located in Mooresboro, in Rutherford and Cleveland Counties, North Carolina. The CSS ash basin system consists of the active ash basin, the Units 1-4 inactive ash basin, and the Unit 5 inactive ash basin, all of which are unlined. Two unlined dry ash storage areas within the ash basin waste boundary and a lined dry ash landfill nearly a mile away from the CSS are located within the footprint of the Unit 5 inactive ash basin. Voluntary groundwater monitoring for the ash basin system began in 1995 and continued until 2011. NPDES compliance groundwater monitoring began in April 2011 with sampling events scheduled three times per year. As required by CAMA, Duke Energy submitted a GAR/CSA in August 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the ash basins and ash storage area. At CSS, groundwater in the shallow, transition, and fractured bedrock flow layers flows from south to north towards the Broad River as does the migration of coal ash related contaminants. This flow direction is generally away from the nearest water supply wells. Groundwater in the shallow and transition zone layers also drains toward Suck Creek then northerly to the Broad River. Horizontal migration to the north is controlled by the Broad River which is a hydrologic boundary. The data indicates that geologic conditions present beneath the ash basins impedes the vertical migration of contaminants. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The horizontal extent of soil contamination is generally limited to the area beneath the ash basins. The vertical extent of soil contamination was determined to be generally limited to the soil sampled beneath the ash basin. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, soil and groundwater impacts are present beneath and downgradient of the ash basins. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site. The CAP Part 1 was submitted in November 2015 to support the DEQ's risk ranking classification for the site's ash basin system. PPBCs are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Dan River The Dan River Steam Station ("DRSS") is owned and formerly operated by Duke Energy Carolinas and is located on the Dan River in Rockingham County near Eden, North Carolina. The DRSS ash basin system consists of a Primary Cell, a Secondary Cell, and associated embankments and outlet works. Two ash storage areas also exist to the north and upgradient of the Primary and Secondary Cells and consist of ash dredged from the Primary Cell. Voluntary groundwater monitoring for the DRSS ash basin began in 2007 and continued until 2010. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. As required by CAMA, Duke Energy submitted a GAR/CSA in August 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the ash basin. At DRSS, groundwater in the shallow, deep, and bedrock flow layers beneath the ash basin predominantly flows south and southeast toward the Dan River, with a northerly component of flow north of Ash Storage 1 towards a drainage feature that ultimately flows south to the Dan River that requires further evaluation. These flow directions are away from the nearest public and private water supply wells. The GAR/CSA found that the direction of migration of coal ash - related contaminants in groundwater is toward the Dan River. The approximate horizontal extent of groundwater impacts is limited to beneath and in the immediate vicinity of the ash basin and ash storage areas. The approximate vertical extent of groundwater impacts includes the shallow, deep, and bedrock flow layers. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The COI concentrations observed in the soil from the various locations within the DRSS site generally bracket the concentrations observed in soil samples from the background locations or within reasonable proximity of the bracketed background concentrations. E A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, groundwater impacts are present beneath and downgradient of the ash basin. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site. The CAP Part 1 was submitted in November 2015 to support the DEQ's risk ranking classification for the DRSS ash basin system. PPBCs are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. HF Lee HF Lee Energy Complex is owned and operated by Duke Energy and is located near the town of Goldsboro, in Wayne County, North Carolina. Five ash storage areas have historically been used to manage ash at the Lee Plant. These are referred to as inactive basins 1, 2, and 3, the `active' basin and the Lay of Land Area ("LOLA"). The inactive basins and the LOLA were used to manage ash from the 1950s until the 1970s when the active basin was built. The `active' basin was used to manage ash until 2012 when the coal-fired units were retired. Groundwater monitoring events related to the NPDES permit for the site are conducted three times per year since 2011. Groundwater in the surficial aquifer under the ash basins flows horizontally to the east and south and discharges into the Neuse River or Halfmile Branch. This flow direction is away from the nearest public and private water wells. The surficial aquifer groundwater discharge to surface water provides a boundary for migration. There are no known users of shallow groundwater downgradient of the ash basins. Private water wells are located upgradient of the ash basins. There are no water supply wells located between the ash basins and the Neuse River. Elevated constituent occurrences in soil ranged from background areas to soil beneath the ash basins. The highest concentrations of cobalt and iron in soil were from a background location north of the inactive basins. Barium and manganese at elevated levels were detected beneath the LOLA. The highest concentrations of thallium and vanadium in soil were detected in shallow soil west of the active basin. The highest concentration of arsenic in soil was from beneath the active basin. The highest concentration of boron in a soil sample was collected from beneath inactive basin 1. The hydrogeologic and geochemical data are consistent with observed conditions that indicate migration of CCR constituents to, and potentially beyond, the compliance boundary is limited to boron and arsenic at the east side of the active basin. The horizontal migration of boron and arsenic in the surficial groundwater best represent the dominant flow and transport system. Downward vertical migration is restricted due to the clay and silt layers beneath the ash basins that act as confining layers over the deeper aquifers in the area. The approximate extent of 10 horizontal migration of boron and arsenic, the constituents that appear to be attributable to migration from the ash management areas are shown on Figures ES -1 a and ES -1 b for the inactive and active ash basin areas. Findings from the Comprehensive Site Assessment at HF Lee Energy Complex indicate that no imminent hazard to human health has been identified as a result of constituent migration from the ash basins or LOLA. Marshall Marshall Steam Station ("MSS") is owned and operated by Duke Energy Carolinas and is located on Lake Norman in Catawba County near the town of Terrell, North Carolina. As required by CAMA, Duke Energy submitted a GAR/CSA in August 2015, characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. For the GAR/CSA, the source area consisted of the ash basin, dry ash landfill (Phases I and 11), and Photovoltaic (PV) structural fill (ash basin system). Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from these CCR management units. Prior to the GAR/CSA, voluntary groundwater monitoring for the MSS ash basin began in November 2007 and continued until October 2011. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. GAR/CSA findings indicated that groundwater in the shallow, deep, and bedrock flow layers beneath the ash basin system flows horizontally from northwest and north to the southeast toward Lake Norman, with a portion beneath the dry ash landfill (Phase 1) flowing to the east- southeast toward an unnamed tributary that flows to Lake Norman as is the migration of coal ash -related contaminants. The groundwater flow direction is away from the nearest private water supply wells. The approximate horizontal extent of groundwater impacts is limited to beneath the ash basin and dry ash landfill (Phase 11), east and downgradient of the ash basin and dry ash landfill (Phase 1), and southeast and downgradient of the ash basin, within the ash basin compliance boundary. The approximate vertical extent of groundwater impacts is generally limited to the shallow and deep flow layers. The GAR/CSA also determined the horizontal and vertical extent of soil impacts at the site. The horizontal extent of soil impacts are limited to the area beneath the ash basin and one location east and downgradient of the dry ash landfill (Phase 1). The vertical extent of soil impacts were determined to be generally limited to the uppermost soil sample collected beneath ash. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. 11 Based on the findings of the GAR/CSA, soil and groundwater impacts are present beneath and downgradient of the source areas. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site and to the west of the site. The CAP Part 1 was submitted in December 2015 to support the DEQ;s risk ranking classification for the site. PPBCs were included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Mayo The Mayo Steam Electric Plant is owned and operated by Duke Energy Progress and is located near Roxboro, North Carolina (Person County). The Mayo Plant began commercial operation in 1983. CCRs have historically been managed in the single on-site ash basin. Discharge from the ash basin is permitted under NPDES permit #NC0038377. In 2013, the Mayo Plant converted from a wet to a dry ash handling system. Beginning in November 2014, CCR has been managed in a newly constructed on-site landfill. In general, three zones of groundwater flow can be described for the Mayo Plant. Saprolite is mostly thin and is almost entirely unsaturated. A partially saturated transition zone is encountered below the surficial zone and is characterized primarily by partially weathered rock of variable thickness. The bedrock flow zone is characterized by the storage and transmission of groundwater in shallow, water -bearing fractures. The primary feature that influences groundwater movement is the topography of the area and location of the ash basin within the former Crutchfield Branch stream valley. The basin acts as an elongated bowl -like feature towards which groundwater flows from the northwest, west, south, and east. Groundwater flows away from the ash basin towards the north-northeast. This flow direction is away from the nearest public and private water wells. Boron is the primary constituent in groundwater detected at concentrations greater than background concentrations and 2L. Boron is detected within a three-dimensional volume beneath and downgradient of the ash basin (Figure ES -1). Vertical migration of constituents is limited. Iron, manganese, and vanadium are ubiquitous in Site groundwater and concentrations greater than the 2L/IMAC and provisional background may be a result of natural leaching from aquifer solids and may not indicate direct influence from the ash basins. To date, boron exceedances of 2L in groundwater have not been detected beyond the property boundary of the Plant. Seep results confirm that groundwater is discharging to Crutchfield Branch. Downstream surface water sample results indicate a reduction in concentrations north of the Plant in Crutchfield Branch. The area to the south of the Plant is serviced by a municipal water line. Private supply wells (22) and one public water supply well (Bethel Hills Baptist Church) may be located within one -half - mile of the Site, including three inactive water supply wells located on the Mayo Plant, in the upgradient direction. 12 Findings from the Comprehensive Site Assessment indicate no imminent hazard to human health or the environment has been identified as a result of metals migration from the Mayo Site ash basin. Riverbend Riverbend Steam Station ("RBSS") is located adjacent to the Mountain Island Lake portion of the Catawba River (Mountain Island Lake) near Mount Holly, Gaston County, North Carolina. The RBSS ash basin system consists of a primary cell, a secondary cell, and associated embankments and outlet works. In addition, a cinder storage area and an ash storage area on the property store ash from station operations prior to the construction of the ash basin as well as ash basin clean-out projects, respectively. Voluntary groundwater monitoring for the ash basin system began in 2008 and continued until 2010. NPDES compliance groundwater monitoring began in 2011 with sampling events scheduled three times per year. As required by CAMA, Duke Energy submitted a GAR/CSA in August 2015. The purpose of the GAR/CSA was to characterizing the extent of contamination resulting from the source area, evaluating chemical and physical characteristics of contaminants, investigating geology and hydrogeology of the site, and examining risk to potential receptors and exposure pathways. Source characterization was performed during the GAR/CSA by sampling ash, ash porewater, ash basin surface water, and ash basin seeps from the active ash basin and inactive ash basin. At RBSS, groundwater in the shallow, deep, and bedrock flow layers beneath the ash basin flows north, northwest and northeast toward Mountain Island Lake as does the migration of coal ash -related contaminants. Public and private wells were not impacted. The approximate horizontal extent of groundwater impacts is limited to beneath the ash basin and immediately downgradient of the ash basin to the north, northwest, and northeast, within the Duke Energy property boundary. The approximate vertical extent of groundwater impacts is generally limited to the shallow and deep flow layers with an isolated exceedance in bedrock. The GAR/CSA also determined the horizontal and vertical extent of soil contamination at the site. The horizontal extent of soil contamination is limited to the area beneath the ash basin and downgradient perimeter of the ash basins. The area west and northwest of the cinder storage area requires further soil characterization. A human health and ecological screening -level risk assessment was also conducted as part of the GAR/CSA. No imminent hazards to human health and the environment were identified during the screening -level risk assessments; however, the results indicated that a site-specific risk assessment may be warranted based on constituents in environmental media. Based on the findings of the GAR/CSA, soil and groundwater impacts are present beneath and downgradient of the ash basin, ash storage area, and the cinder storage area. Some constituent exceedances in soil and groundwater appear to be naturally occurring. Data gaps, identified in the GAR/CSA, are currently being addressed to better understand groundwater quality and flow characteristics at the site and to the west of the site. The CAP Part 1 was submitted in November 2015 to support the DEQ's risk ranking classification for the site's ash basin system. 13 PPBCs are included in CAP Part 1 to better understand soil and groundwater impacts at the site by comparison to naturally occurring conditions. Roxboro The Roxboro Steam Electric Plant is owned and operated by Duke Energy Progress and is located near the town of Roxboro, in Person County, North Carolina. The ash management area consists of the two ash basins: the semi -active East Ash Basin, the active West Ash Basin and a lined landfill. An unlined landfill was constructed on top of the semi -active East Ash Basin in the late 1980s. Discharges from the ash basins are permitted under NPDES Permit NC0003425. The NPDES permit authorizes discharge from the facility to Hyco Reservoir. Regional groundwater flow at the Site is to the west/northwest toward the Hyco Reservoir. The water table at the Site is typically located within a transition zone above bedrock or within bedrock. Groundwater in both zones generally flows north/northwest across the Site to the Hyco Reservoir. A discharge canal and topographic ridge located west of the Site ash basins limits groundwater flow in that direction. Localized groundwater high zones are centered around the ash basins, with radial flow in these areas. The GAR/CSA determined that soils beneath the ash basins and across the Site have not been greatly affected by the ash basins. While there are numerous detections in soils of COls above the RSL, the exceedances at background locations are comparable to those detected in soils beneath the ash. Therefore, it is questionable whether these exceedances can be attributed to operation of the ash basin. Groundwater impact from ash pore water seepage is limited to beneath the ash basins and downgradient in the areas between the ash basins and Hyco Reservoir and the intake canal. The boron plume depicted in the Executive Summary Figure 1 is the most conservative area for the plume based on common constituents found to be indicative of potential coal ash contamination. Seeps represent preferential pathways of ash pore water migration to surface water, however most appear to drain to the NPDES discharge, with the exception of S-14 in the area of the Gypsum Pad, which appears to discharge to the intake canal. No public supply wells were located in the Site area except a well located at the dry wall plant located east of the Site, across the intake canal and two located at an elementary school located southwest and upgradient of the Site. No private drinking water wells, or wellhead protection areas, were found to be located within the potential area of interest downgradient of the ash basins. Findings from the Comprehensive Site Assessment at the Site lead to the conclusions that there is no imminent hazard to human health or the environment due to soil or groundwater impacts at the site. Sutton The L.V. Sutton Energy Complex (Site) is owned and operated by Duke Energy Progress and is located in Wilmington, New Hanover County, North Carolina. The ash management area consists of the former ash disposal area ("FADA"), the unlined 1971 ash basin and the lined 1984 ash basin. Both the FADA and 1971 basin contain saturated ash; the bottom of the 1971 14 basin is approximately 35 to 40 feet below the water table. A cooling pond (Lake Sutton) is located adjacent to the basins to the west. CCR generation ceased in 2013 and all ash will be removed from the Site in accordance with CAMA. During coal sluicing operations, water was discharged from the 1971 and 1984 ash basins to the cooling pond under an NPDES permit. Currently, the Site operates under an NPDES Permit which authorizes discharge of cooling pond blowdown, recirculated cooling water, noncontact cooling water, and treated wastewater, which is collected in the basins and discharged to a final outfall on the Cape Fear River. Regional groundwater flow is to the west toward the Cape Fear River, to the east toward the Northeast Cape Fear River or to the south toward the convergence of the two rivers. In the vicinity of the 1971 and 1984 ash basins, groundwater flows radially. A groundwater divide is located northeast of the ash basins and groundwater north of the basins flow west toward the cooling pond. Groundwater east and south of the basins flows east, southeast and south. In the FADA, groundwater flows to the southwest. The GAR/CSA indicated that horizontal groundwater impact is delineated by monitor wells on- site to the north and south of the ash basins onsite and off-site to the east. Wells could not be installed west of the ash basins due to the presence of the cooling pond and Cape Fear River. Vertical delineation has been defined in the upper portion of the Pee Dee Formation, assuming chloride concentrations and specific conductance levels in the lower Pee Dee wells are indicative of salt water intrusion and account for the boron concentrations detected at that level. Additional wells are planned for the lower Pee Dee to confirm these observations. Thirty-two private water wells were identified within 0.5 mile of the Site compliance boundary during the GAR/CSA. Two public supply wells are located on adjacent property to the east. These two water supply wells will be abandoned once the area is connected to the City of Wilmington municipal water system. This is expected to be completed by first quarter 2016. Groundwater extraction wells are also being planned along the eastern Site boundary to prevent further migration. Weatherspoon Weatherspoon Power Plant, located near the town of Lumberton in Robeson County, North Carolina, is owned and operated by Duke Energy Progress to produce back-up electricity from gas-fired generators. Coal-fired boilers were decommissioned in 2011 and subsequently demolished. Boiler ash from past operations was managed in a single ash basin. Current triannual groundwater monitoring under NPDES permit conditions began in November 2010. Groundwater monitoring of the Weatherspoon ash basin was performed under the plant NPDES permit from 1990 to 1998 and on a voluntary basis from fall 2006 until spring 2010. The Weatherspoon ash basin was constructed with raised perimeter dikes. GAR/CSA data indicate that the ash is situated above the predicted post -closure water table. Infiltration of ash pore water from the basin into the underlying soils has resulted in a well-defined zone of groundwater impacted with boron. A small portion of the impacted zone ("plume") exhibits 15 arsenic contamination. Iron, manganese, and vanadium are ubiquitous in GAR/CSA groundwater samples, making it difficult to determine if concentrations of these parameters in the plume are increased by releases from the ash basin. Groundwater flow in the vicinity of the Weatherspoon ash basin is primarily to the southeast with radial flow components to the northeast and southwest. Flow of unaffected groundwater from the northwest is displacing the plume beneath the ash basin. Groundwater flow from the vicinity of the ash basin discharges to the plant cooling pond to the southeast, a short stretch of Jacob Creek to the east, and ultimately the Lumber River to the south. Downward flow into underlying water supply aquifer is inhibited by a low permeability confining layer across the Weatherspoon Plant site. Shallow subsurface hydrology is the primary factor that controls the slow movement of contaminants in groundwater. Immobilization by precipitation or sorption appears to limit the movement of trace metals such as arsenic but has limited effect on boron. Public water supply wells are located several miles from the ash basin in an upgradient direction. Private wells sampled by NC DEQ do not exhibit concentrations of potential pollutants in excess of provisional background concentrations presented in the Corrective Action Plan Part 1 (CAP 1). GAR/CSA data indicate that horizontal and vertical soil contamination related to the ash basin is limited to the immediate vicinity of the basin. Areas of soil and groundwater contamination unrelated to the ash basin were identified during the GAR/CSA. Weatherspoon GAR/CSA and CAP 1 findings identified no imminent hazard to human health or the environment due to soil or groundwater impacts at the site. No data gaps were identified after compilation of the GAR/CSA. A limited number of soil samples will be collected and analyzed to provide data for the evaluation of monitored natural attenuation using US EPA methodology to be presented in the CAP Part 2. Section 4 — Status of Ongoinq Work North Carolina General Statutes § 130A-309.21 1 (b)(1)(f) requires that groundwater CAPs include, in addition to the specific listed elements, "[a]ny other information related to groundwater assessment required by the Department. ,3 In accordance with this provision, the Department has requested additional information, and Duke Energy has begun the process of collecting it. Supplemental information will be included in the CAP Part 2s scheduled for submission by the CAMA deadline, set by the Department at 180 days from submission of the GAR/CSAs. Although, the additional information requested may provide added precision to the data already collected, there is no reason to believe that it will materially change the conclusions drawn from the existing data. Supplemental Investigation, Monitoring and Analysis Based on the ongoing work and communications with DEQ, Duke Energy is currently conducting supplemental groundwater investigations by performing additional borings; installing additional groundwater monitoring wells; collecting additional groundwater, surface water, and 3 The Department is still bound by the Administrative Procedure Act not to make information requests that are arbitrary and capricious. 16 seep samples; and collecting geophysical data. Duke Energy estimates around 150 additional borings and/or monitoring wells will be installed across the 14 sites (approximately 45 at Duke Energy Progress sites and 105 at Duke Energy Carolinas sites). Most of the locations were identified based on a review of the initial site investigation data collected pursuant to the approved GAPs and discussions with DEQ's Division of Water Resources ("DWR") regional staff. The actual number and placement of the wells have been, or will be, reviewed with regional DEQ staff for input prior to installation. In general, supplemental investigation activities focus on improving site knowledge by: identification of site areas where additional precision on groundwater flow or groundwater quality is desired, installation of additional background groundwater quality monitoring wells to more precisely quantify naturally occurring background levels, and collection of additional geophysical data. The approximate proposed locations for the additional borings and monitoring well locations are shown on the figures found in Appendix 4.1. Additionally, Duke Energy and its consultants are continuing to evaluate the incorporation and analysis of additional data into the groundwater models. Corrective Action Plan Part 2s By agreement with the Department, the CAPs were prepared in two parts. As authorized by the Department in accordance with G.S. 130A -309.211(a)(1), Part 2 of each CAP will be submitted no later than 180 days from the submission of the GAR/CSAs. Until the Part 2s have been submitted and the Department has reviewed the results, it would be premature for the Department to draw conclusions about the adequacy of the information presented therein. Duke Energy and its professional consultants prepared the CAP Part 1 reports in a form consistent with the pertinent provisions of G.S. 130A -309.211(b), 15A N.C.A.C. 2L.01 06(f), and applicable guidance documents to provide a summary of site usage; a summary of the GAR/CSA findings; a description of exceedances of groundwater standards, including exceedances attributable to natural background conditions (as assessed against PPBCs based on available data); an evaluation and refinement of COls for modeling purposes; a detailed description of the site conceptual model ("SCM"); results of the groundwater flow and transport model; and results of the groundwater to surface water interaction model. Sample tables of contents for two CAP Part 1 reports are included in Appendix 4.2. The CAP Part 2 will include refined SCM information, a human health and ecological risk assessment (either as an attachment or under separate cover), proposed alternative methods for achieving groundwater quality restoration, conceptual plans for recommended corrective action, an estimated implementation schedule, and a plan for future monitoring and reporting. The scope of the CAP Part 2 report was developed in consultation with DWR Draft tables of contents for two CAP Part 2 reports are included in Appendix 4.3. 17 Section 5 — Additional Data Duke Energy, in conjunction with DEQ, has agreed to complete an additional two rounds of sampling, referred to sample sets 3 and 4. Duke Energy has recently received final analytical results for sample set 3. Field sampling for sample set four is underway and analysis will be completed in late January 2016. Sampling data from sample sets one, two, and three can be found in Appendix 5 for all 14 stations. Section 6 — Responses to Comments On November 17, 2015, DEQ provided a memo that describes "an overview of issues identified to date that are obstacles to restoration of groundwater quality at the coal ash facilities." Duke Energy is providing responses to those comments here and will provide additional information in the CAP Part 2s. Nonetheless, to be clear, the Department's identification of additional information that would be useful in assessing these sites is not evidence that Duke Energy has not complied with CAMA. Duke Energy's obligations under § 130A -309.211(a) were to (1) submit assessment plans, (b) implement approved assessment plans, and (c) submit reports describing exceedances of groundwater standards associated with the impoundments. Duke Energy has demonstrably satisfied each of these requirements. The deadline has not yet arrived for full compliance with § 130A -309.211(b); however, Duke Energy is on schedule to submit CAPs that contain all of the elements in subsection (b)(1). Department Comment: 1. Data that have been clearly identified as needed to complete site assessments have not been addressed at all facilities and have not been incorporated in groundwater models or preliminary remedial design. Remedial design will be incomplete until significant data gaps are addressed. Duke Energy Response: Duke Energy has agreed to address "data gaps" identified in the Department's review of the GAR/CSAs by including additional information in the CAPs and/or supplemental submittals as appropriate. Nonetheless, the extensive data collected to -date is sufficient for the selection of remedial options as well as the initial remedial design. The remedial design will be refined to reflect additional data collected in the future. While the nature of subsurface investigation is iterative, and additional information provides additional precision to the understanding of site conditions, there is no basis for concluding that additional information will change any parameter material to the CAPs or selection of an appropriate remedy, nor has the Department affirmatively stated that it believes there is such a basis. Department Comment: 2. For the most part, provisional background determinations for groundwater were not statistically derived; instead, ranges of concentrations were identified with typically the highest concentration detected chosen as representative of background. Since provisional background concentrations of groundwater constituents have not been adequately established, the 2L Standards and IMAC exceedances cannot be confirmed at this time. Duke Energy Response: Although Duke Energy intends to provide statistical analyses supporting a determination of background concentrations of groundwater constituents, such analyses are not a requirement of CAMA or necessary for the development of a CAP. First, a statistical analysis of background concentrations is not necessary to make a technically valid determination of the impacts attributable to the ash basins. The SCMs for these sites, which are consistent with the science and the site-specific data, state that groundwater contaminants move outward from the basins, that they travel in the direction of groundwater flow, and that they travel at various relative speeds, with boron and sulfate as the fastest travelers. As the Department has stressed, these SCMs are of primary importance in site assessment and CAP development. According to the SCM, groundwater exceedances that are outside the boron plume surrounding the impoundment do not reflect a signature consistent with coal ash impacts, or are upgradient from the impoundment, and are not attributable to the impoundment. It is not necessary to have a statistical analysis of background data to reach this conclusion. Second, as the Department is aware, the timing imposed by CAMA has made it physically impossible for Duke Energy to include seasonality in samples collected or collect sufficient data to conduct a robust statistical analysis at all sites. The vast majority of the groundwater wells providing data were installed in 2015. A recognized artifact of well installation is initially high turbidity, which equalizes over time. The Department required that sample results from background wells where turbidity was greater than 10 NTU be removed from the data set used to determine site-specific provisional background concentrations. As a result, the newly installed wells have not provided sufficient data for a statistical analysis. For locations where compliance boundary background wells provide sufficient data (8 or more sampling events) and with turbidity results below 10 NTU, statistical analyses were used to develop provisional background concentrations. Due to the number of sampling events, this analysis could only be performed for constituents historically analyzed in the pre-CAMA NPDES groundwater monitoring program. However, in the Work Plan approval letters DEQ added constituents to the required sampling for the CSAs that were not historically included in the NPDES monitoring. For these additional constituents there have been only 1 to 2 sampling events, which is an insufficient number of sample events to perform statistics. Also, for some sites, the Department has used recent monitoring data to question whether the compliance boundary background wells are representative of background conditions. Duke 19 Energy was asked to not use the compliance background well data in the provisional background evaluations at this time. This exclusion of data further reduced the data available for computation of provision background concentrations. For these situations, the Department and Duke Energy have discussed the need to develop non -statistically -derived provisional background concentrations for submittal in CAP Part 1 with development of statistically derived provisional background concentrations as sufficient data is collected over time. It is understood that these background concentrations are provisional until DEQ makes a final determination with respect to background concentrations. For informational purposes, the background data has been subjected to a number of different computational methods, and there has not been a default to the highest value. Each consultant, one for Duke Energy Progress and Duke Energy Carolina, computed background concentrations based on available data for each site. Methods and presentation of the data differ between the consultants, but the overall approach is very similar. Each consultant prepared a document to explain the reasoning behind the computational methods. The results of these computations are presented in Appendix 6.1. The computational approach to background concentrations in the CAP Part 1 s was appropriate for the amount of data available at that time. Provisionally, use of the highest value is not without technical justification when the SCM indicates that that the groundwater wells are of sufficient distance from the impoundments to be unimpacted; any lower value results in the counterintuitive conclusion that a background well is exceeding the naturally -occurring background concentration. These provisional background concentrations will be refined as additional data is available. Nonetheless, proposed background concentrations are not necessary to the development of site prioritizations or for remedial action selection at this point in time. Duke Energy will work with the Department to develop the background concentrations as more data is available. Further, the Department correctly points out in their comments that these provisional background concentrations are generated for the limited purpose of determining exceedances of 2L Standards and IMAC exceedances as a result of impoundment operation. Provisional background values are not intended primarily for evaluation of background conditions in offsite drinking water supply wells nor should they be the primary basis for such an evaluation. Accordingly, Duke Energy has relied on other sources of information to assess risks to off-site drinking water wells. Department Comment: 3. The fate and transport models generated to date to address 2L Standards and IMAC exceedances only incorporated a limited number of groundwater constituents. As a result, models that depict distribution of impacted groundwater are incomplete. 20 Duke Energy Response: Constituents selected for the fate and transport models were those that were determined by the university -based modeling team to be source -related, based on the SCM, with analytical results that exceeded applicable regulatory criteria, and with a distribution not suggestive of naturally occurring conditions. The selection of constituents used for modeling will be reviewed for the modeling performed in CAP Part 2. The basis for selection or exclusion of particular constituents is clearly documented in the CAP Part 1 s. Appendix 6.2 presents a table of constituents for each site showing which were selected for modeling and the reason for exclusion of those that were not. Department Comment 4. The relationship of potential coal ash constituents detected in private and public water supply wells with respect to the coal ash impoundments has not been adequately evaluated at facilities where there are nearby receptors. Duke Energy Response: The CSAs provide extensive data on the direction of groundwater flow and the migration of contaminants from the impoundments. During the course of these detailed investigations, no information has been identified to suggest impacts to receptors except for potential impacts previously identified adjacent to the Sutton and Asheville plants and appropriate actions are being implemented for these two sites. The SCMs indicate that such impacts would not occur based on measured site conditions, and there are no alternative SCMs supported by the data that do suggest potential impacts. Additionally, the review of independent drinking water data presented in Section 9 below indicates that the results found to date in nearby drinking water wells are not consistent with impacts from coal ash. Section 7 — Review and Commentary: Groundwater Assessment and Corrective Action GAR/CSAs and CAP Part 1 s provide the Department data and analysis as needed for the separate tasks of (a) approval of corrective action, and (b) classification of impoundments. These reports provide information collected over a finite duration, i.e., an approximately six month period during 2015. Likewise, these reports focused on the collection of data from specific locations, i.e., on-site. As such, this commentary provides a discussion of potential concerns that would influence report conclusions in time and space. These concerns include the (1) mounding of ash basin water, (2) presence of fractured rock, (3) influence of pumping from off-site wells, (4) depth of sampling versus depth of off-site wells, (5) the potential for a change in prevailing site geochemistry, (6) the importance of ash which remains submerged in groundwater, and (7) the basis of selecting COls for modeling. The intent of this section is to define and summarize each concern, at a generalized high level, in the context of GAR/CSA and CAP part 1 conclusions. The process of geotechnical and geological investigation is iterative in terms of data collection and analysis. Subsequent iterations during the evolving corrective action process will increase the resolution of data and associated conclusions. 21 Mounding This concern refers to the extent to which ash ponds raise or variably influence the natural potentiometric surface, causing flow to leave the basin radially, and against the prevailing slope aquifer gradient. In particular, the question is whether at any time (past, present, or future) the effects of mounding have resulted in advective transport of ash constituents to off-site well receptors. Topographical and monitoring well data establish the extent to which localized mounded water creates hydraulic gradients that influence groundwater direction. The GAR/CSAs demonstrate that while localized mounded gradients exist, they occur within a larger slope aquifer system. As such, this system still controls the overall site gradient and groundwater flow remains away from off-site well receptors. Mounding is contained within and defined by hydraulic boundaries including topographical divides, drainage features (streams), and groundwater discharge locations. In terms of time, historical operations of ash basins were managed within narrow tolerances. For example, ash basin elevations have been controlled with hydraulic structures (e.g., stop logs), typically within a couple feet. Future operation will involve dewatering, and as such, less mounding. Deep fractures This concern refers to the extent to which fractures and fissures could potentially be present that could then serve as a conduit between off site water wells and ash constituents. Off-site drinking water wells are generally installed in bedrock so the concern would focus on whether an undetected continuous channel could exist between bedrock wells and groundwater impacted by ash constituents. GAR/CSA data have not revealed karst-like features which would support a continuous channel that conveys groundwater against the prevailing down-slope direction. More broadly, the nature and extent of fractured rock is such that it follows the well-established Slope Aquifer conceptual model.4 Bedrock aquifers in the piedmont are hydraulically connected to the overlying transition zone and surficial aquifers, and they all slope toward a discharge location (river or lake). The presence of fractures will influence the rate, but groundwater flow is ultimately in the same down-slope direction, i.e., toward a river or lake and away from off-site receptor wells. Also, in the Piedmont, fractures are irregular and discontinuous, not tending to form a continuous conduit. Further, coal ash constituents are dissolved in water with no measurable increase in density, as compared to other contaminants which would tend to "sink" in the aquifer, such as dense non aqueous phase liquids or saltwater. Moreover, GAR/CSA data indicate that groundwater flow is primarily lateral, not vertically downward. As such, coal ash constituents travel with the predominantly lateral flow direction, rather than travelling vertically toward the bedrock. This is 4 LeGrand, H.E., 2004, A master conceptual model for hydrogeological site characterization in the Piedmont and Mountain region of North Carolina, a guidance manual: Raleigh, North Carolina Department of Environment and Natural Resources, Division of Water Quality, Groundwater Section, 50 P. 22 consistent with GAR/CSA data which indicate less impact of ash constituents with depth, with little to none in bedrock, depending on the site. Pumping This concern refers to the extent to which off-site wells influence the prevailing groundwater flow direction, potentially drawing in coal ash constituents within their respective capture zone. In general, the net effect of any pumping by off-site wells on hydraulic gradient is detected by the existing network of GAR/CSA monitoring wells, as well as the calibrated model. These data nor the model indicates a general, site -wide influence. A preliminary capture zone analysis confirms that virtually all off-site wells are defined by capture zones which remain off site. (See Groundwater Flow and Transport Modeling Technical Memorandum in Appendix 7.) Apart from the L.V. Sutton Energy Complex, a review of off-site well water quality data does not reveal an impact by boron or other EPA Appendix III constituents. Off-site drinking water wells are generally installed in bedrock. GAR/CSA data indicate less impacts from ash with depth, with little to none in bedrock, depending on the site. Depth of GAR/CSA wells versus receptor wells This concern compares the depth of wells installed for purposes of the GAR/CSA versus the likely depth of off-site wells. Off-site wells are typically installed much deeper in bedrock as compared to the bedrock sampling in the GAR/CSA. Coal ash constituents are not driven by density (i.e., they do not sink like dense non -aqueous phase liquids) but rather move by lateral advection and dispersion, away from off-site receptors. Additionally, groundwater predominantly flows laterally and not vertically, as indicated by very low amounts of boron found in bedrock wells. Contamination will usually discharge to a surface water body before traveling to great depths. Thus, there is no theoretical basis for assuming that constituents of concern have traveled to the depths accessed by off-site wells. Further, the data indicate that the vertical extent of ash impacts remains at or above the level of bedrock sampling reported in the GAR/CSA. If contaminants were migrating to deeper locations in the bedrock, then the existing bedrock monitoring wells would have detected this migration, since the contaminants would have to first migrate through the zones accessed by these monitoring wells. Changes in Geochemistry The concern is that changes in Eh/pH, because of operational activity (capping, dewatering, etc.), will result in greater/different releases of soluble constituents from ash or from soil. In the case of soil, the concern is that while the constituents may be naturally occurring, they are being released because of site activity. In either circumstance, a change in site conditions could change the concentration and type of contaminant beyond that currently identified. The GAR/CSAs indicate that actual site pH/Eh conditions are relatively stable. Data indicate that sites are generally acidic and oxidizing, with localized variations. Potential corrective action 23 scenarios do not create the basis for dramatic changes in geochemistry as controlled by Eh and pH. For example, the direction of travel remains the same, i.e., away from off-site wells. The GAR/CSAs do not indicate that these sites have hydrocarbons which would give rise to dramatic oxidation/reduction reactions. For example, they are devoid of constituents (e.g., benzene, solid waste leachate) which would be biodegraded, thus consuming electron acceptors (such as oxygen, nitrate, etc.) and lead to reducing conditions. Similarly, these sites do not exhibit acid mine drainage conditions. Saturated Ash The concern is that ash cannot be allowed to remain submerged within groundwater, since the ash is a source of contamination. The impacts of leaving in place are appropriately addressed through the corrective action planning process. Neither the groundwater assessment process nor the corrective action planning process neglects the presence of submerged ash as a source of constituents of concern or assumes that that ash will have no effect. Groundwater assessment provides information about current site conditions, which make possible conclusions about the rate of migration of constituents of concern over time Data are interpreted in accordance with SCMs built around the concept that submerged ash is a source of those constituents to the groundwater. Corrective action planning is based in part on modelling of future conditions, including comparing cap -in-place scenarios, which involve engineered changes to movement of groundwater through saturated ash, and excavation scenarios, in which the ash is removed. A statement that submerged ash potentially serves as a continuing source of contaminants to groundwater reflects a first -level understanding of site conditions that leaves out many of the complexities of site dynamics. A more complete understanding of a site recognizes that the submerged ash must leach and leached constituents must migrate. Not all ash constituents are leachable nor do they all migrate at the same rate. To the extent that leaching and transport occurs, it is observed in monitoring well data. Further, as well documented in the scientific literature, leachable material is exhaustible and source concentrations decrease with time. Duke Energy's technical experts have used models that capture these dynamics, calibrated with measured site data. In some cases, the models use conservative assumptions, such as using a constant source concentration. Thus, the effects of leaving ash submerged in groundwater have been, and will continue to be, assessed with state of the art analytical techniques and will be incorporated into corrective action planning. Constituent Modeling The concern is that not enough constituents were modeled and/or the basis on which they were selected is not clear. All constituents which had an identifiable nexus with the ash basins were modeled. For any given site, this group of constituents varies, according to site variability. As many as 13 constituents were modeled for some sites. 24 Naturally occurring soil and ash are both sources of groundwater exceedances of 2L standards, and as such professional judgment is required to separate the two. Professional judgment was applied and peer reviewed by licensed engineers and scientists at universities, consulting firms, the National Ash Management Advisory Board, Duke Energy, and the Electric Power Research Institute. Groundwater modeling was not performed to predict naturally occurring constituents. As noted in the Groundwater Flow and Transport Modeling Technical Memorandum found in Appendix 7, models predict the contaminant flow field, with ash basins as the source, with confidence. Section 8 - Responses to Comments from Others Duke Energy was copied on comments submitted to DEQ by SELC on several of the CSAs. Duke Energy requested that the technical consultants who prepared each of the CSAs review the comments and provide a response. Those responses are included in Appendix 8. Section 9 — Evaluation of DEQ Drinking Water Data Additional analyses conducted by Duke Energy for submittal in the CAP Part 2s further support a conclusion that off-site drinking water wells are not impacted at most sites. As an initial point, off-site drinking water wells were not selected by DEQ for sampling based on a SCM that suggested they were likely to be impacted by migration of contaminants from ash basins or that predicted the COls based on ash basin chemistry. Instead, the wells were conservatively selected primarily based on their distance from the ash basins without an assessment of whether the wells were hydrologically upgradient or downgradient from the basins. The drinking water sampling program included analyses for a wide range of constituents, some of which are commonly considered as indicators of contamination from coal ash impoundments and some of which are far less common in coal ash and not generally considered to be coal ash indicators. As expected based on literature and historical drinking water well sampling conducted by others, the Department's drinking water sampling program yielded results which included detections of many compounds which are often naturally -occurring in NC groundwater. In order to put these analytical results in context and evaluate whether there is any indication of drinking water well contamination from the coal ash impoundments, Duke Energy commissioned a study of the available data by Dr. Lisa Bradley, PhD of Haley & Aldrich, this report was submitted to the Department on December 17, 2015 and an abbreviated version, without figures or appendices, is included in Appendix 9. Dr. Bradley's analysis further supports the lack of an impact to off-site wells. It is not possible to identify if a well has been impacted by a release from a coal ash management unit using a single metric. This is due in large part to the fact that all of the constituents that are present in coal ash and that could be released to groundwater are naturally occurring. The challenge is to understand these background conditions, and in that context, evaluate whether there has been an impact from a release from coal ash. Based on an understanding of the behavior of constituents that can be released from coal ash into groundwater, USEPA has identified those constituents that are considered together to be indicators of a potential release from coal ash; these are the CCR Rule Appendix III 25 constituents. Of these, boron and sulfate are the most common constituents used to evaluate the potential for an impact in groundwater. To understand if a particular well or wells have been impacted by a release from a coal ash management unit, the following are needed: An evaluation of the magnitude of concentrations of the constituents in the well, An evaluation of those detected constituents in relation to background concentrations in groundwater, An evaluation of the potential correlation between the co -presence and concentration of constituents considered to be indicators of a release from a coal ash management unit, and Consideration of the information available on the potential for there to be a complete transport pathway between a coal ash management unit and a well. The attached report has evaluated the DEQ private well results in the following ways: By constituent and by facility, In the context of four sets of screening levels for drinking water, In the context of background, both regional and national, In the context of the CCR Rule Appendix III constituents that are considered to be indicators of potential release from coal ash management units to groundwater, and In the context of the groundwater assessments conducted as part of the GAR/CSA for each facility. The results for boron, sulfate and calcium are not suggestive of a release of constituents from coal ash management units to groundwater in these private well areas. There are few instances of the USEPA CCR Rule Appendix IV and other constituents above screening levels, and in most cases, the private well results are within the range of background, as discussed in Section 5. There are two non -Appendix IV constituents that consistently exceed DHSS screening levels. Vanadium exceeds DHHS and 2L screening levels in almost all wells; however, all results are below the tapwater RSL and all results are below background levels. Hexavalent is above the DHHS screening level for all samples; however, the majority are within the range of background as discussed in Section 5.3.3 and shown on Figure 14c. Neither vanadium nor hexavalent chromium is commonly identified as a coal ash indicator, and neither is correlated with known coal ash indicators in the private well data. Accordingly, it is unlikely that the presence of vanadium or hexavalent chromium in the wells is derived from coal ash. The GAR/CSAs for each of the facilities have demonstrated that groundwater is flowing away from residential areas in the vicinity of the facilities. Thus taken together, and with the exception of Sutton, the results do not indicate an impact of coal ash management units at Duke facilities on private wells. 26 Section 10 - Closure Alternatives In reviewing site data and other factors in anticipation of classifying the ash basins, it is useful to take a broad look at the future impact on site groundwater activities in the context of site classification. There are two primary differences between a classification of "low" and a classification of "high" or "intermediate" — timing and closure alternatives. The timing of the classifications varies by five years for each incremental level of risk — high (2019 closure), intermediate (2024 closure), and low (2029 closure). A classification of high or intermediate mandates closure by removal. A low risk classification allows closure by removal or by capping in place. Any closure by removal brings with it high associated costs and community impacts, therefore, before classifying a site as high/intermediate, it should be firmly established that there is a commensurate reduction in environmental risk to warrant the added costs and community impacts. The best way to evaluate this environmental risk reduction (or lack thereof) with respect to groundwater issues is through the site modeling. Details of the groundwater modeling demonstrate two key points which are essential to evaluating the relative environmental risk posed by various site closure options: If (hypothetically) no action is taken at the site, the groundwater conditions remain essentially unchanged for the indefinite future. Stated another way, the groundwater system is essentially in a steady state condition, and, if no changes in operating conditions occur, there are no significant changes anticipated in the extent of contamination. This can be seen by an inspection of the current conditions model results and the model results for the "no action" scenario for future years. (See, for example, slides 12 (Allen) and 17 (Roxboro) in Appendix 1.) The plume is not expected to grow in intensity or magnitude over time if no action is taken. (Of course, this "no action" assumption is extremely conservative given the plans in the near future to begin dewatering of the basins to reduce the driving head and thereby reduce the groundwater impacts.) This inspection of model simulations indicates that the timing of site closure is relatively unimportant from the perspective of groundwater impacts. Whether basin closure (source control) is performed by excavation or by capping in place the result with respect to groundwater is substantially the same. This can be seen by an inspection of the future model simulations for groundwater conditions for the two closure scenarios (removal and capping). These model scenarios indicate that the groundwater experiences similar benefits from either closure scenario suggesting that the important factor is that dewatering and closure are performed rather than the particular closure method chosen. Further, it is worthy of note that the approach to an impacted receptor (if an impacted receptor is identified or a receptor is significantly threatened) would be expeditious drinking water replacement along with targeted groundwater remediation. The solution would not be excavation. It would take far too long and cause far too many ancillary negative impacts to the community. It is highly unlikely that the response would be a change in source control. Stated another way, since the method of source control (closure) appears to have little bearing on 27 groundwater impacts, there appears to be no groundwater -based driver for preferring one method over another. Conclusion Information collected and submitted to the Department in GAR/CSAs and CAP Part 2s shows that most of Duke Energy's ash basin sites do not pose an imminent hazard to human health or the environment. Site groundwater flow at most sites is away from off-site receptors, even after the effects of mounding and pumping and the potential for deep bedrock flow are accounted for in the analysis. Off-site private water supply well water quality data is inconsistent with an impact from coal ash, since concentrations of constituents of concern are not correlated with coal ash indicator constituents and are in the range of measured background. Corrective action assessment and planning are ongoing, and further data will be shared with the Department as it becomes available. However, SCMs and existing information indicate that such data may add precision to site measurements but will not materially affect the understanding of groundwater flow and migration of contaminants. Details of the groundwater modeling demonstrate that: (1) even in the absence of corrective action, groundwater conditions are expected to remain essentially unchanged for the indefinite future; and (2) closure by excavation and by capping in place result in very similar future site conditions. As a result, regardless of whether excavation is required for closure, it is not expected to be the best way to address groundwater. Impacts to receptors (if there were any) would be more effectively addressed by providing replacement drinking water and conducting targeted groundwater remediation than by excavation, which would take longer and create ancillary negative impacts to the surrounding community. Duke Energy's efforts to date have complied with CAMA's groundwater assessment and corrective action provisions. Information generated is sufficient to provide a substantial record on which the Department can rely to develop proposed classifications for the basins. Nonetheless, Duke Energy remains committed to working with the Department to continue to collect information and to provide analyses that generate more precise descriptions of site conditions and risks. : Appendices 1. Presentation 2. CAMA Requirements 3. Executive Summaries 4. Ongoing Work 4.1 Additional Well Locations 4.2 Sample CAP Part 1 TOCs 4.3 Sample CAP Part 2 TOCs 5. Additional Data 6. Response to DEQ Comments 6.1 Background Calculations 6.2 Model Tables 7. Responses to Other Comments 7.1 Drinking Water Well Model Runs 8. Responses to SELC Comments 8.1 HDR response to Allen, Buck, and Marshall comments 8.2 Synterra response to Mayo comments 8.3 Synterra response to Roxboro comments 9. Bradley Report 29