NC0005088_Final GAP Approval Letter_20150219

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NCDENR
North Carolina Department of Environment and Natural Resources
Pat McCrory
Governor
February 19, 2015
Mr. Harry Sideris
Senior Vice -President
Environment, Health, and Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, NC 28202
Re: Cliffside Steam Station
Donald R. van der Vaart
Secretary
NPDES Permit No. NC0005088 — Rutherford and Cleveland Counties, North Carolina
Conditional Approval of Revised Groundwater Assessment Work Plan
Dear Mr. Sideris:
On December 31, 2014, the Division of Water Resources (Division) received the revised
Groundwater Assessment Plan (GAP) for the above listed facility. The revised GAP was submitted
in response to the Division's Review of Groundwater Assessment Work Plan letter dated November
4, 2014 regarding requirements of the Coal Ash Management Act 2014 — G.S. 130A -309.209(a). A
review of the plan has been completed and several deficiencies or items requiring clarification were
noted. In order to keep the site assessment activities on a timely schedule, the Division has approved
the revised GAP under the condition that the following deficient items are addressed in the
Groundwater Assessment Report:
• Comment Section 5.3 Hydrogeologic Site Characteristics:
The initial site conceptual site model (ISCM) section of the revised GAP does not provide a
clear, cohesive description of how constituents of potential concern (COPCs) may migrate
from the source(s) to the receptors through various pathways. It is acknowledged that there
is information available to develop an ICSM, but data are not presented in a manner such as
groundwater elevation maps, geologic maps, cross-sections that depict detailed site
conditions, flow diagrams, or in a tabulated format to illustrate where data gaps may exist.
Duke Energy should incorporate all existing data at the site and be prepared to collect
additional data if the Division determines that additional data gaps exist. Continued site
conceptual model development should follow guidelines similar to those presented in the
American Standards Testing Measures E1689 - 95(2014) Standard Guide for Developing
Conceptual Site Models for Contaminated Sites to direct data collection, data interpretation,
and model development efforts.
Two detailed hydrogeologic and groundwater chemistry reports for the Cliffside facility
were not cited or referenced in the revised GAP. The reports, titled "Co -management of
1636 Mail Service Center, Raleigh, North Carolina 27699-1636
Phone: [phone] \ Internet: hitp://www.ncwater.org
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Coal Combustion By -Products and Low -Volume Wastes: A Southeastern Site" (Electric
Power Research Institute, EN -7545, 1991) and "Field Evaluation of Utility Low -Volume
Wastes with High -Volume Coal Combustion By -Products: CL Site" (Electric Power
Research Institute, TR -108242, 1997), contain information and data relevant to the
proposed site assessment and should be used in conceptual site understanding, site
assessment, and comprehensive site assessment (CSA) report development.
Information in the report titled "Characterization of White Material Observed in Seepage,
Inactive Ash Basin #5 Main Dam (Ruthe-070), Cliffside Steam Station" (HDR
Engineering, Inc. of the Carolinas, April 11, 2014) should be used in the site assessment
and documented in the CSA report. If other reports relevant to groundwater
contamination and (or) hydrogeologic assessment exist, they should also be used and
documented in the CSA report.
• Comment Section 7.0 Site Assessment
Duke Energy proposes to evaluate background Fe and Mn conditions and potential
anomalies in compliance well data prior to installing additional wells needed to delineate
the extent of elevated Fe and Mn. To meet the CSA and CAP deadlines mandated by the
Coal Ash Management Act, Duke should install the wells needed for Fe and Mn
delineation upon revised GAP approval. Any efforts to evaluate historic data may be
performed in conjunction with the installation and sampling of new wells.
• Comment Section 7.1.1 Ash and Soil Borings:
For borings outside ash basins and ash storage areas, the revised GAP states that
laboratory analyses performed on these samples will depend on the nature and quantity of
material collected. It is expected that for the locations sampled, a solid phase sample will
be collected and analyzed for inorganics at each sampled interval (soil/saprolite just
above the water table, soil/saprolite just below the water table, transition zone, and
bedrock fractures).
• Comment Section 7.1.2 Groundwater Monitoring Wells:
Shallow monitor wells proposed in the revised GAP text do not match the quantity of
shallow wells proposed in Table 8. Please verify the quantities of all proposed wells
(shallow, deep, and bedrock) contained in the revised GAP text, Table 8, and Figure 3
and inform the Regional Office via email the correct amounts for each.
Move well cluster GWA-21 to a location immediately adjacent to the toe drain of the
active ash pond dam, an area where elevated concentrations of COPCs are likely.
Analytical results from seeps in this vicinity have displayed elevated concentrations of
boron and other COPCs.
• Comment Section 7.1.4 Bedrock Monitoring Wells
Add the following bedrock well locations: a) AB-4BR, b) IB-4BR, c) U54BR, and d)
GWA-21 BR to address data gaps at these locations both within the ash basins and at the
toe of the active pond.

• Comment Section 7.2 Groundwater Sampling and Analysis:
Direction provided in the EPA Region 1 Low Stress Purging and Sampling Procedure for
the Collection of Groundwater Samples from Monitoring Wells (2010) should be
followed strictly and any deviations from the procedure must be approved by the
Division and documented accordingly. For example, samples should not be collected
until pH is stabilized within f 0.1 for three consecutive readings rather than f 0.2 written
in the GAP. Temperature and specific conductivity readings should stabilize within 3%
for three consecutive readings before samples are collected instead of 10% noted in the
GAP. Also note that if the pumping rate is so low that the flow-through-cell/chamber
volume cannot be replaced within a 5 minute interval, the time between measurements
should be increased accordingly.
The proposed monitor well locations in and around Unit 5 appear to be appropriate for
purposes of groundwater assessment in this area of the site. However, this does not
constitute or imply approval of locations for purposes of NPDES compliance monitoring
of the Unit 5 Inactive Ash Basin. For more information please contact the Regional
Office.
For purposes of radium/uranium groundwater sampling: a) add locations U5-4S/D/BR,
AB-3S/SL/D, and BG-1S/D/BR and b) remove MW -11D and BG-3S/D.
• Comment Section 7.2.1 Compliance and Voluntary Monitoring Wells:
It is expected that all compliance wells and a subset of voluntary monitor wells will be
sampled and analyzed as part of the site assessment.
• Comment Section 7.7.5 Domain of Conceptual Flow Model:
Suck Creek should be included as a hydrologic feature in groundwater flow and transport
modeling to account for potential contaminant transport to the creek and for mass fluxes
in and out of the model domain. If it appears that groundwater containing constituents
above the 2L standards is discharging to Suck Creek, it is expected that transect data
collection and modeling be carried out as discussed in the general comment section of
this letter.
• Comment Section 9.0 CSA Report:
Provide the following additional maps in the CSA report: a) a shaded relief map created
from LIDAR digital elevation models and b) a site wide orthophoto map showing soil fill
areas. Include site boundaries, impoundments, and all facility and water supply wells on
both maps. Information from the North Carolina Division of Energy, Mineral and Land
Resources regarding basin and dam construction should be incorporated, as applicable,
into the site assessment report.
See comment 39 in the Division's Review of Groundwater Assessment Work Plan letter
dated November 4, 2014 for a list of the geologic cross sections that the Division would
like to see presented in the CSA report. In addition, each source -to -receptor transect
proposed for geochemical or other modeling should also be represented by a geologic
cross section.

In addition, technical direction that will serve as the basis of expectations for completion of the site
assessment is provided at Attachment 1. Failure to address the deficient items stated above will
result in Duke Energy not being in compliance with the stated statutes. Per G.S. 130A -309.209(a)
(3) and (4), you must begin implementation of the revised GAP on March 1, 2015 and the
Groundwater Assessment Report is due on August 18, 2015. It is our understanding that Duke
Energy may have to obtain additional permits to facilitate installation of certain monitoring wells. In
the event permits are needed for this purpose, Duke Energy should take all steps necessary consistent
with the law to avoid delaying completion of the assessment report.
If you have any questions, please contact Ted Campbell at [phone].
Sincerely,
S. Jay Zimmerman, P.G., Acting Director
Division of Water Resources
cc: WQROS — ARO
WQROS Central Files
DENR Secretary - Don van der Vaart
HDR (Attn: William Miller) 440 South Church Street, Suite 1000, Charlotte, NC 28202

Attachment 1
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Duke Energy GAP Review Issues
The items identified in this Groundwater Assessment Plan (GAP) review summary are provided for
general discussion for the various parties to agree upon technical direction and content in the revised
GAPs, comprehensive site assessments (CSAs), and corrective action plans (CAPS).
Groundwater Monitoring
1. A schedule for continued groundwater monitoring is mandated by the Coal Ash Management
Act 2014. An interim plan should include at least two rounds of groundwater samples collected
and analyzed in 2015. The analytical results of the first round of data collected in 2015 would be
included in the CSA report, while the results of the second round would be submitted as a CSA
addendum. After CSA data can be evaluated, a plan for continued groundwater monitoring can
be developed for implementation in 2016.
2. Sites impacted by inorganics are typically managed using a tiered site analysis which includes
four elements a's referenced in EPA/600/R-07/139:
• Demonstration of active contaminant removal from groundwater & dissolved plume
stability;
• Determination of the mechanism and rate of attenuation;
• Determination of the long-term capacity for attenuation and stability of immobilized
contaminants, before, during, and after any proposed remedial activities; and
• Design of performance monitoring program, including defining triggers for assessing
the remedial action strategy failure, and establishing a contingency plan.
This reference and the framework described above should be used as applicable to meet
the corrective action requirements found in 15A NCAC 02L.0106.
3. Because of uncertainty concerning the site's ability to attenuate contaminants over the long
term given potentially changing geochemical conditions, there is a need to address the elements
of the tiered site analysis described above and collect appropriate samples as part of the CSA,
CAP development, and continued groundwater monitoring.
4. The Division of Water Resources (Division) Director is responsible for establishing background
levels for COPCs in groundwater. This determination is based on information and data provided
by the responsible party and may include formal statistical testing using background wells with
at least four rounds of data. Wells identified as "background" are subject to periodic review
based on a refined understanding of site chemistry and hydrogeologic conditions. In general,
each facility must have a background well or wells screened or open to each of the dominant
flow systems that occur at the site and are associated with groundwater contamination. Any
questions concerning adequacy of background monitoring locations or conditions at the
facilities should be directed to the Regional offices.

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5. Delineation of the groundwater contaminant plume associated with coal combustion residuals is
a requirement of the investigation and if off-site monitoring wells are ultimately required to
perform this task, then it is expected that these activities will be completed as part of the
groundwater assessment activities and included in the final report. Documentation of the effort
to gain off-site access, or right of way permits, will be provided if off-site access is denied or
alternate means of assessing the area were not available within the allocated timeframe (such
as within right-of-ways).
Site Assessment
Data Requirements and Sampling Strategy
1. Robust data collection is warranted to support timely completion of site assessments and
subsequent corrective action plans because of the impending deadlines for completion of CSAs
and OAPs, scale and geologic complexity of the sites, the challenges of modeling heterogeneous
systems, and site proximity to potential human and sensitive ecosystem receptors.
2. Robust data collection will be focused along strategically positioned flowpath transect(s) - from
ash pond source to potential receptor—as an efficient approach for model development
(analytical, geochemical, groundwater flow, and transport) in support of risk assessment and
CAP development. Data collected to support evaluation of site conditions along the flowpath
transects should be located along or defensibly proximate to the modeled transects.
3. The dataset developed along proposed flowpath transects will include any information needed
to determine constituent concentrations, conduct Kd tests, and perform batch geochemical
modeling in multiple flow horizons as appropriate. This data will include a) solid phase sample
collection for Kd measurement and batch geochemical modeling, inorganic analysis and
speciation, and other parameters identified in General Comment #4 of the November 4, 2014
GAP comments issued by DWR, b) solution phase sample collection for total and dissolved
inorganic analysis of total concentrations, small pore filtration for dissolved samples, etc., and c)
slug, constant/falling head, and packer testing. The solid phase sample mineralogy, total
concentration results, re-dox measurements, and other geochemical parameters will be used as
input for equilibrium speciation calculations of redox sensitive constituents calculated by
PHREEQC or similar program (EPA/540/5-92/018). This geochemical modeling will be performed
to identify potential mineral phases, estimated species speciation and concentrations, and will
be performed varying key solubility controlling parameters to predict mineral phases,
speciation, and concentrations under varying conditions. Solid samples for Kd tests from
locations where moderately to strongly reducing conditions are anticipated shall be frozen upon
collection and tested in glove box conditions (EPA/600/R-06/112). Refer to EPA/600/R-07/139
Section III forthe data collection and characterization needed to support the four -tiered analysis
discussed above.
4. Speciations for groundwater and surface water samples should include Fe, Mn, and any COPCs
whose speciation state may affect toxicity or mobility (e.g. As, Cr, Se, or others if applicable).
This speciation will apply for groundwater samples collected at wells located along proposed

Attachment 1
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flowpath transects and in wells where these constituents exceed 2L groundwater standards as
well as for surface water samples collected within ash impoundments.
5. Solid phase samples shall be analyzed for: minerals present, chemical composition of oxides,
hydrous Fe, Mn, and AL oxides content; moisture content; particle size analysis; plasticity;
specific gravity; porosity; permeability, or other physical properties or analyses needed to
provide input to a chosen model. The Division reserves the right to request analysis for organic
carbon content, organic carbonate content (as appropriate if site conditions warrant), or ion
exchange capacities, if needed to complete the site assessment process.
6. In addition to conducting the SPLP leachable inorganic compounds analysis for selected ash
samples to evaluate the potential for leaching of constituents to groundwater, the leachable
analysis should also be conducted for some soil samples from locations beneath the ash ponds,
within the plume, and outside the plume to evaluate potential contributions from native soils.
7. In addition to collecting solid phase samples onsite for Kd procedures, soil samples should be
also collected from unaffected soils within groundwater flow pathway to evaluate Kd(s) or
hydrous ferrous oxide.
8. Rock samples for laboratory analyses should be collected as commented in General Comment 4
of the November 4, 2014 GAP comments issued by DWR. This GAP review comment indicated
that the sample(s) collected from bedrock well soil and rock cores shall be analyzed, at a
minimum, for the following: type of material, formation from which it came, minerals present,
chemical composition as oxides, hydrous Fe, Mn, and Al oxides content, surface area, moisture
content, etc.; however, these analyses were not mentioned in the GAP. The Division reserves
the right to request analysis for organic carbon content, organic carbonate content, and ion
exchange capacity if needed to complete the site assessment process.
9. The coal ash and soil analyte lists should match the groundwater analyte lists.
10. Total uranium analysis should be analyzed where total radium is analyzed for groundwater.
11. If analytical results from a seep sample exceed 2L standards, then the area in the vicinity of the
sample location should be investigated for groundwater contamination. If analytical results
from a surface water sample exceed 2B standards, then the area in the vicinity of the sample
location should be investigated for groundwater contamination.
12. Surface water/seep samples should be collected during baseflow conditions and that the
groundwater monitoring (WLs and sampling) should occur at about the same time.
13. Measurement of streamflow in selected perennial streams is expected as needed in support of
simulation/calibration of flow and transport models; major rivers that serve as groundwater
divides are not included in this expectation.
Conceptual Model Elements
1. In the CSA report, data gaps remaining should be specifically identified and summarized.
2. Site heterogeneities should be identified and described with respect to: a) their nature, b)
their scale and density, c) the extent to which the data collection successfully characterizes
them, d) how the modeling accounts for them, e) and how they affect modeling uncertainty.

Attachment 1
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3. The impact of data gaps and site heterogeneities should be described in relation to the
elements developed in the Site Hydrogeologic Conceptual Model and Fate and Transport
Model subsections.
4. For sites in the Piedmont or Mountains, the CSA Report should include a subsection within the
Site Geology and Hydrogeology Section titled 'Structural Geology'. This section should
describe: a) foliations, b) shear zones, c) fracture trace analysis, and d) other structural
components anticipated to be relevant to flow and contaminant transport at the site.
5. Duke Energy will include a poster -sized sheet(s) (ANSI E) combining tabulated analytical
assessment results (groundwater, surface water, and leachate samples); multiple sheets may
be needed to present the data. This should be provided in addition to the individual analytical
results tables that will be prepared for the CSA reports. Any questions concerning format or
content of the analytical result summaries should be directed to the Regional offices.
Geochemical Modeling
1. The Division agrees that a geochemical model "coupled" to a 3-D fate and transport model is
inappropriate given the size and complexity of the sites and the extremely large amount of data
required to calibrate such a model. Rather, a "batch" geochemical model approach should be
sufficient for successfully completing the site assessment and/or corrective action plan.
2. Samples collected for "batch" geochemical analysis should be focused along or defensibly
proximate to flowpath transects.
3. To support successful batch geochemical modeling, dissolved groundwater samples collected
along a contaminant flowpath transect should be obtained using a 0.1 um filter. This will help
ensure a true dissolved phase sample. Note that the dissolved samples are for assessment
purposes only and may not be used for purposes of compliance monitoring. If there is
uncertainty about which areas/wells will be used in the batch geochemical modeling, the initial
round of assessment sampling at the facility can utilize the 0.45 um filter until the contaminant
flow path transects are selected. Once determined, Duke Energy can go back and re -sample the
wells needed for geochemical modeling using the 0.1 um filter. It is recognized that the use of a
0.1 um filter will be difficult for wells'with elevated turbidity; in this case, it is recommended,
that Duke Energy use two filters in series (the water initially passes through a 0.45 um filter to
remove larger particles prior to passing through the 0.1 um filter). Information for a disposable
0.1um field filter designed specifically for sampling groundwater for metal analysis is provided at
the following link: http://www.vosstech.com/index.php/products/filters. If field comparisons of
0.1 versus 0.45 micron filtration at several transect wells at a given site show no significant
differences between the two methods, then 0.45 micron filters may be used for evaluating the
dissolved phase concentrations at that site.
4. In support of the objectives of General Comment #2 of the November 4, 2014 GAP comments
issued by DWR , Duke Energy should add a column titled 'relative redox' to the analytical results
tables to record the geochemical conditions for that location/sample date. The redox
determination should be based on observed DO, ORP, and any other relevant measures and
presented for historic and new samples (wells, ash pore water, surface waters, etc.). Relative

Attachment 1
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redox designations may include "iron reducing", "sulfate reducing", mildly oxidizing, moderately
oxidizing, etc. and should be footnoted with a statement about the degree of confidence in the
designation based on amount and quality of available data.
5. Duke Energy shall also evaluate: a) spatial geochemical trends across the facility and along
selected flow paths, b) temporal geochemical trends where observable (such as for compliance
boundary wells), along with the likely reason for the change (e.g. increase in seasonal recharge,
pond de -watering and subsequent reversal of groundwater flow direction, inundation of well
from river at flood stage, etc.) in support of the CAP. This evaluation step will require a
comparison of geochemical conditions overtime with rainfall data, notable ash capping,
dewatering, disposal/removal, or other plant operations, etc. The quality of existing
geochemical data will be evaluated using field notes, calibration records, and consistency in
redox measurements (e.g. eH vs. raw ORP).
Groundwater Models
1. The technical direction for developing the fate and transport modeling will follow guidelines
found in Groundwater Modeling Policy, NCDENR DWQ, May 31, 2007, and discussions
conducted between Duke Energy and their consultants with the Division. Ultimate direction for
completion of fate and transport models will be provided by the Division.
2. The CAP Report should include a subsection within Groundwater Modeling Results titled 'Site
Conceptual Model' that succinctly summarizes, for purposes of model construction, the
understanding of the physical and chemical setting of the site and shall include, at a
minimum: a) the site setting (hydrogeology, dominant flow zones, heterogeneities, areas of
pronounced vertical head gradients, areas of recharge and discharge, spatial distribution of
geochemical conditions across the site, and other factors as appropriate), b) source areas and
estimated mass loading history, c) receptors, d) chemical behavior of COPCs, and f) likely
retention mechanisms for COPCs and how the mechanisms are expected to respond to changes
in geochemical conditions.
3. Modeling will be included in the Corrective Action Plan (CAP). The four -tiered analysis
previously referenced and appropriate modeling should be conducted, and the mass flux
calculations described in the EPA/600/R-07/139 should be performed.
4. The CAP Report shall provide separate subsections for reporting groundwater flow models and
fate and transport models.
5. The CAP Report should include subsections within Groundwater Modeling Results titled
'Groundwater Model Development' that describes, for each chosen model: a) purpose of model,
built-in assumptions, model extent, grid, layers, boundary conditions, initial conditions, and
others as listed in Division guidance. Include in this section a discussion of heterogeneities and
how the model(s) account for this (e.g. dual porosity modeling, equivalent porous media
approach, etc.). Separate subsections should be developed for the groundwater flow model,
fate and transport model, and batch geochemical models, respectively.
6. CAP Reports should include a subsection within Groundwater Modeling Results titled
'Groundwater Model Calibration' that describes, for each model used, the process used to

Attachment 1
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calibrate the model, the zones of input and calibration variables (for example, hydraulic
conductivities) that were used, the actual (measured) versus modeled results for all key
variables, and others. Separate subsections should be developed for the groundwater flow
model, fate and transport model, and batch geochemical model(s), respectively.
7. CAP Reports should include a subsection within Groundwater Modeling Results titled
'Groundwater Model Sensitivity Analysis' that describes, for each model used, the process used
to evaluate model uncertainty, variable ranges tested, and the key sensitivities. Separate
subsections should be developed for the groundwater flow model, fate and transport model,
and batch geochemical model(s), respectively.
Development of Kd Terms
1. Kd testing and modeling in support of CAP development should include all COPCs found above
the NCAC 15A 02L .0106(8) standards in ash leachate, ash pore water, or compliance boundary
well groundwater samples.
2. The selected Kd used in transport modeling often will profoundly affect the results. Duke
Energy should acknowledge this concept and document within the transport modeling section(s)
of the CAP all widely recognized limitations inherent in the estimation of the Kd term.
Risk Assessment
1. Provide references for guidance and potential sampling methodology related to conducting a
baseline ecological risk assessment or habitat assessment, if warranted.