NC0003468_Other_20160503

(> DUKE
ENERGY.
April 28, 2016
Jeffrey O. Poupart
Water Quality Permitting Section Chief
Division of Water Resources
Department of Environmental Quality
State of North Carolina
1617 Mail Service Center
Raleigh, NC 27699-1617
Harry K. Sidens
Senior Vice President
Environmental, Health & Safety
526 S Church Street
Mail Code EC3XP
Charlotte, NC 28202
[phone]
Subject: March 2, 2016 Insufficiency of Discharge Assessment Plans - Duke Energy Carolinas,
LLC and Duke Energy Progress, LLC
Dear Mr. Poupart:
This responds to your letter of March 2, 2016 to Duke Energy Carolinas, LLC and Duke Energy
Progress, LLC on March 2, 2016 regarding Duke Energy's proposed Discharge Assessment
Plans.
With regard to your letter describing changes in Section 3.2.2 Observation and Sampling:
• The discussion must include a statement noting that jurisdictional determinations regarding
the extent of waters of the United States and their relationship with identified seeps at the
subject facilities will be obtained from the United States Army Corps of Engineers (USA
COE).
Duke Energy does not yet have jurisdictional determinations from the US Army Corps of
Engineers for the relevant areas at all of the twelve sites mentioned in your letter. We submitted
applications for jurisdictional determinations in September, October, and November 2015 and
have since worked with the Corps of Engineers to schedule site visits and provide draft plats for
approval. Nonetheless, the timing of the approved jurisdictional determinations is up to the
Corps and outside of Duke's control. To date, out of these twelve sites, only Buck has an
approved jurisdictional determination, but we do not yet have the signed plats.
We will submit the maps you have requested for each site on a rolling basis, within a reasonable
period after the jurisdictional determinations are complete. In order to address the changes
described in your March 2, 2016 letter, we have added the following text at the start of Section
3.2.2.
Jurisdictional determinations regarding the extent of waters of the United States and
their relationship with identified seeps at the subject facilities will be obtained from the
United States Army Corps of Engineers (USA COE). Until jurisdictional determinations
are finalized by USA COE, preliminary information will be used to evaluate the seeps as
described in the section below.
RECEIVED/NCDEQ/DWR
MAY 0 3 1016
Water Quality
Permitting Section

J
J
The second change in Section 3.2.2 described in your letter is as follows.
The schedule for water quality sampling of the seeps and related jurisdictional waters must
be more frequent than the semi-annual basis stated in the proposed DAPS. DWR
recommends a monthly monitoring schedule, consistent with the conditions described in the
DAPs' general assessment requirements, for all identified seeps that will continue for twelve
(12) months. After that time, monitoring may be reduced to a semi-annual basis until such
monitoring becomes a requirement of the NPDES permit.
We do not believe sampling monthly as part of a revised Discharge Assessment Plan is
warranted. For the larger receiving waters, data is available from sampling associated with
NPDES permits that demonstrates the lack of impact on the larger surface waters of the state.
In addition, we are conducting weekly observations of all AOWs on a dam or dike slope,
sampling any new seeps, and providing the analytical results to DEQ. We recommend the
sampling frequency under the DAPs remain at twice/year with the weekly inspections of dam
slopes for any new seeps with data provided to DEQ. We recommend that we collectively focus
our resources on the completion of all of the NPDES Wastewater Permits for the Duke Energy
sites and implement appropriate sampling frequency for each of the permitted seeps in that
document.
However, in order to address the changes described in your March 2, 2016 letter, we have
added the following text in Section 3.2.2.
In addition to sampling conducted with the semi-annual assessments, additional seep
P 9
sampling will be conducted at locations and at a frequency as determined through
discussions with NC DEO personnel.
We would like to work with DEQ to achieve alignment of the various (present and future)
documents involving required seep activities including:
• Discharge Assessment Plans
• Discharge Identification Plans
• NPDES Wastewater Permits
• EPA requirements
• Any future legal agreements with either DEQ or EPA
Duke Energy is committed to providing the Department with additional information to facilitate
the issuance of new NPDES Wastewater permits. The issues are complex and require special
consideration, as illustrated by the time elapsed since the permit applications were submitted.
We look forward to working with you further to resolve the issues identified here on a mutually
acceptable schedule.
Sincerely,
Harry Sideris
Senior Vice President
Environmental, Health and Safety

Dan River Combined Cycle Station Ash Basin
Topographic Map and
Discharge Assessment Plan
NPDES Permit NC0003468
April 29, 2016

Duke Energy Carolinas, LLC I Discharge Assessment Plan �1J�
Dan River Combined Cycle Station Ash Basin
CONTENTS
Contents
Page
Contents.......................................................................
Figures and Tables .......................................................
Section1 - Introduction.............................................................................................................. 1
Section2 - Site Background....................................................................................................... 3
2.1 Plant Description..................................................................................................3
2.2 Ash Basin Description..........................................................................................3
2.3 Site Geologic/Soil Framework..............................................................................4
2.4 Topographic Map and Identification of Discharges...............................................5
2.4.1 Engineered Drainage System for Earthen Dam........................................5
2.4.2 Non -Engineered Seep Identification.........................................................6
Section 3 - Discharge Assessment Plan..................................................................................... 7
3.1 Purpose of Assessment.......................................................................................7
3.2 Assessment Procedure........................................................................................7
3.2.1 General Assessment Requirements.........................................................7
3.2.2 Observation and Sampling.......................................................................8
3.2.3 Evaluation..............................................................................................10
3.2.4 Assessment Reporting...........................................................................10
Section4 - References..............................................................................................................11

Duke Energy Carolinas, LLC I Discharge Assessment Plan ���
Dan River Combined Cycle Station Ash Basin
FIGURES AND TABLES
Figures and Tables
Figure 1 — Site Location Map
Figure 2 — Topographic Map
Table 1 — Seep and Associated Discharge Locations and Descriptions
Table 2 — Laboratory Analytical Methods
Table 3 — Dan River Combined Cycle Station — Example of Surface Water/Seep Monitoring
Flow and Analysis Results Table

Duke Energy Carolinas, LLC I Discharge Assessment Plan Dan River Co�11
Combined Cycle Station Ash Basin J
.I SECTION 1 - INTRODUCTION
Section 1 - Introduction
The purpose of this document is to address the requirements of North Carolina General Statute
(GS)130A-309.210(a) topographic map and (b) Assessment of Discharges from Coal
Combustion Residuals Surface Impoundments to the Surface Waters of the State, as modified
by North Carolina Senate Bill 729, for the Dan River Combined Cycle Station (DRCCS) ash
basin operated under National Pollutant Discharge Elimination System (NPDES) Permit
NC0003468.
The following requirements are contained in General Statute (GS) 130A-309.210(a):
(1) The owner of a coal combustion residuals surface impoundment shall identify all
discharges from the impoundment as provided in this subsection. The requirements for
identifying all discharges from an impoundment set out in this subsection are in addition
to any other requirements for identifying discharges applicable to the owners of coal
combustion residuals surface impoundments.
(2) No later than December 31, 2014, the owner of a coal combustion residuals surface
impoundment shall submit a topographic map that identifies the location of all (i)
outfalls from engineered channels designed or improved for the purpose of collecting
water from the toe of the impoundment and (ii) seeps and weeps discharging from the
impoundment that are not captured by engineered channels designed or improved for
the purpose of collecting water from the toe of the impoundment to the Department.
The topographic map shall comply with all of the following:
a. Be at a scale as required by the Department.
I'
b. Specify the latitude and longitude of each toe drain outfall, seep, and weep.
c. Specify whether the discharge from each toe drain outfall, seep, and weep is
continuous or intermittent.
d. Provide an average flow measurement of the discharge from each toe drain outfall,
seep, and weep including a description of the method used to measure average flow.
e. Specify whether the discharge from each toe drain outfall, seep, and weep identified
reaches the surface waters of the State. If the discharge from a toe drain outfall,
seep, or weep reaches the surface waters of the State, the map shall specify the
latitude and longitude of where the discharge reaches the surface waters of the
State.
f. Include any other information related to the topographic map required by the
Department.
The following requirements are contained in General Statute (GS) 130A-309.210(b):
b) Assessment of Discharges from Coal Combustion Residuals Surface Impoundments to
the Surface Waters of the State. The owner of a coal combustion residuals surface

i'
Duke Energy Carolinas, LLC I Discharge Assessment Plan �1J�
Dan River Combined Cycle Station Ash Basin
SECTION 1 - INTRODUCTION
impoundment shall conduct an assessment of discharges from the coal combustion
residuals surface impoundment to the surface waters of the State as provided in this
subsection. The requirements for assessment of discharges from the coal combustion
residuals surface impoundment to the surface waters of the State set out in this
subsection are in addition to any other requirements for the assessment of discharges
from coal combustion residuals surface impoundments to surface waters of the State
applicable to the owners of coal combustion residuals surface impoundments.
(1) No later than December 31, 2014, the owner of a coal combustion residuals surface
impoundment shall submit a proposed Discharge Assessment Plan to the
Department. The Discharge Assessment Plan shall include information sufficient to
allow the Department to determine whether any discharge, including a discharge
from a toe drain outfall, seep, or weep, has reached the surface waters of the State
and has caused a violation of surface water quality standards. The Discharge
Assessment Plan shall include, at a minimum, all of the following:
a. Upstream and downstream sampling locations within all channels that could
potentially carry a discharge.
b. A description of the surface water quality analyses that will be performed.
c. A sampling schedule, including frequency and duration of sampling activities.
d. Reporting requirements.
e. Any other information related to the identification of new discharges required by
the Department.
(2) The Department shall approve the Discharge Assessment Plan if it determines that
the Plan complies with the requirements of this subsection and will be sufficient to
protect public health, safety, and welfare; the environment, and natural resources.
(3) No later than 30 days from the approval of the Discharge Assessment Plan, the
owner shall begin implementation of the Plan in accordance with the Plan's
schedule.
The North Carolina Senate Bill 729 establishes the submittal date of this topographic map and
Discharge Assessment Plan no later than December 31, 2014.
The topographic map, developed to satisfy the requirements of GS130A-309.21-0(a), was
utilized as the basis for developing the assessment procedures presented in this plan, required
by GS1 30A-309.21 0(b).
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Duke Energy Carolinas, LLC I Discharge Assessment Plan 01
Dan River Combined Cycle Station Ash Basin
SECTION 2 -SITE BACKGROUND
Section 2 - Site Background
2.1 Plant Description
Dan River Steam Station (DRSS) was a coal-fired generating facility located near the town of
Eden in Rockingham County, North Carolina. The three -unit station began commercial
operation in 1949. All three coal-fired units, along with three oil -fired combustion turbine units,
were retired in 2012 and are currently being decommissioned. Simultaneously, the DRCCS, a
620-megawatt natural gas facility, began commercial operations on site on December 10, 2012.
The Dan River site is located on the north bank of the Dan River, and the surrounding area
j generally consists of undeveloped and agricultural land, the Dan River, and a small number of
residential properties (Figure 1).
2.2 Ash BasinDescription
The ash basin system is located adjacent to the Dan River and consists of a Primary Cell, a
Secondary Cell, and associated embankments and outlet works, as shown on Figure 2. The ash
basin is impounded by earthen dikes and an earthen/ash divider dike separates the Primary Cell
from the Secondary Cell. The Primary Cell lies at an elevation of approximately 535 feet and
has a surface area of approximately 21.8 acres. The Secondary Cell lies at an elevation of
approximately 527 feet and has a surface area of approximately 12.2 acres.
The original ash basin was constructed in 1956 with an approximate crest elevation of 525 feet.
In 1968 and 1969, the ash storage basin was expanded to cover the area occupied today. At
that time, the dikes were raised to an approximate elevation of 530 feet. In 1976 and 1977, the
intermediate dike was constructed to stage sluicing by subdividing the basin into a Primary Cell
and Secondary Cell. The intermediate dike and new Primary Cell dikes were vertically
expanded through inward dike construction, where the outward dike slope was maintained and
extended upward to the dike crest. Through inward dike construction, portions of the main dike
were constructed over ash. The intermediate dike was also constructed over ash.
In 1980, newer dikes, referenced as the dredge dikes, were constructed north of the Primary
j and Secondary Ponds, creating a dredge pond and two dry storage areas. Ash was dredged to
!_ the southernmost portion of the northern ash fill and free liquids were allowed to gravity drain to
the topographically lower dredge pond located between the dry storage areas. Once dewatered,
ash was hauled and placed dry in the two dry storage areas known as Ash Fill 1 and Ash Fill 2.
The placement of ash in the ash storage areas occurred during multiple projects.
The ash basin was operated as an integral part of the site's wastewater treatment system.
During operation of the coal-fired units, the ash basin received variable inflows from the ash
removal system, station yard drain sump, stormwater flows, and other permitted discharges.
The coal ash was sluiced to the southwest corner of the Primary Cell on a variable basis (i.e.,
dependent on DRSS operations) via sluice pipes.
Flow is routed from the Primary Cell to the Secondary Cell through a concrete discharge tower.
Effluent from the Secondary Cell is routed to the Dan River via a concrete discharge tower

Duke Energy Carolinas, LLC I Discharge Assessment Plan ���
Dan River Combined Cycle Station Ash Basin
j SECTION 2 - SITE BACKGROUND
located in the Secondary Cell. The water surface in both the Primary and Secondary Cells is
controlled by the use of stoplogs.
2.3 Site Geologic/Soil Framework
The Dan River site is located within the Piedmont province. The Piedmont is bounded to the
east and southeast by the Atlantic Coastal Plain and to the west by the escarpment of the Blue
Ridge Mountains, covering a distance of 150 to 225 miles (LeGrand, 2004).
The topography of the Piedmont region is characterized by low, rounded hills and long, rolling,
northeast -southwest trending ridges (Heath, 1984). Stream valley to ridge relief in most areas
ranges from 75 to 200 feet. Along the Coastal Plain boundary, the Piedmont region rises from
an elevation of 300 feet msl to the base of the Blue Ridge Mountains at an elevation of
1,500feet msl (LeGrand, 2004).
The Piedmont region is underlain by bedrock of Precambrian and Paleozoic age comprised of
igneous and metamorphosed igneous and sedimentary rocks (Heath, 1984). The predominant
rock types are gneisses, schists, and metamorphosed granitic rocks (LeGrand, 2004) with
undeformed, unmetamorphosed plutonic rocks also present throughout the Piedmont. These
formations are oriented with the regional geologic structure in parallel belts trending northeast
southwest. Throughout the Piedmont, the bedrock is overlain by a variably thick regolith that can
consist of any or all of the following horizons: the residual soil, in -situ, clay -rich weathered rock
referred to as saprolite, and alluvial deposits (Heath, 1984).
The Dan River site is located in the Triassic Dan River Basin located just north of the contact of
the Milton Terrane and the Basin. Locally, the Milton terrane is represented by a Precambrian
metasedimentary unit consisting of metagraywacke and muscovite-biotite schist. The rocks of
the Dan River Basin were deposited within a graben formed between the Piedmont terrane and
the Milton terrane (LeGrand, 1988). Stratigraphy within the basin consists of a lower sequence
of mainly arkosic, coarse -grained sandstone and conglomerate passing upward into siltstone
(Pine Hall Formation), a middle sequence of fossiliferous sandstone, carbonaceous shale, and
thin coal beds (Cow Branch Formation); and an upper sequence of siltstone, arkosic sandstone,
pebbly sandstone, mudstone, and conglomerate (Stoneville Formation; Carpenter, 1982).
Alluvial deposits consisting of unconsolidated sand, silt, and clay with occasional sub -rounded
to well-rounded pebbles occur along the Dan River and major tributaries.
Groundwater occurs within the basin in a system of two interconnected layers: residuum and
weathered rock overlying fractured bedrock. Underlying sandstone layers with the Triassic
sequence likely have some porosity capable of water storage but are generally not used for
water supply. Typically, the residuum is saturated and the water table fluctuates in response to
varying recharge and discharge within it. Lateral movement of groundwater typically occurs in
the weathered rock and fractured bedrock.

Duke Energy Carolinas, LLC I Discharge Assessment Plan ��9
Dan River Combined Cycle Station Ash Basin
SECTION 2 -SITE BACKGROUND
The Dan River site is generally bounded to the south by the earthen dike and a natural ridge on
�i the north bank of the Dan River. The geology/groundwater conditions at the site are expected
to be generally consistent with the characteristics of the conceptual groundwater model
developed by LeGrand for the Piedmont region.
2.4 Topographic Map and Identification of Discharges
A topographic map is presented in Figure 2 to meet the requirements of GS 130A-309.210(a) in
the identification of outfalls from engineered channels, as well as seeps and weeps.
Seepage is the movement of wastewater from the ash basin through the ash basin
l embankment, the embankment foundation, the embankment abutments, basin rim, through
residual material in areas adjacent to the ash basin. A seep is defined in this document as an
expression of seepage at the ground surface. A weep is understood to have the same meaning
as a seep.
Indicators of seepage include areas where water is observed on the ground surface and/or
where vegetation suggests the presence of seepage. Seepage can emerge anywhere on the
downstream face, beyond the toe, or on the downstream abutments at elevations below normal
pool. Seepage may vary in appearance from a "soft," wet area to a flowing "spring." Seepage
may show up first as only an area where the vegetation is lusher and darker green than
surrounding vegetation. Cattails, reeds, mosses, and other marsh vegetation often become
established in a seepage area. However, in many instances, indicators of seeps do not
necessarily indicate the presence of seeps. Areas of apparent iron staining and/or excess iron
bacteria may also indicate the presence of a seep.
Locations of seepage at the ground surface adjacent to the ash basin have been identified and
are shown in Figure 2. These areas include the earthen embankment which impound the ash
basin as well as adjacent areas where water from the ash basin may have infiltrated into the
underlying residual materials and expressed as seepage.
2.4.1 Engineered Drainage System for Earthen Dam
Earth dams are subject to seepage through the embankment, foundation, and abutments.
Seepage control is necessary to prevent excessive uplift pressures, instability of the
downstream slope, piping through the embankment and/or foundation, and erosion of material
by migration into open joints in the foundation and abutments. The control of seepage is
performed by the use of engineered drains such as blanket drains, trench drains, and/or toe
drains. In certain cases, horizontal pipes may be installed into the embankment to collect and
control seepage. It is standard engineering practice to collect the seepage and convey seepage
away from the dam.
The Dan River site ash basin dams (ROCKI-237 and ROCKI-238) were constructed with a
drainage system, which is monitored by Duke Energy. The drainage features, or outfalls,
associated with the ash basin dam are shown as required by GS 130A-309.210(a)(2)(i) on
Figure 2.
pit

Duke Energy Carolinas, LLC I Discharge Assessment Plan �1J�
Dan River Combined Cycle Station Ash Basin
SECTION 2 - SITE BACKGROUND
2.4.2 Non -Engineered Seep Identification
Topographic maps of the site were reviewed to identify regions of the site where there was a
potential for ash basin related seepage to be present. These regions were determined by
comparing ash basin full pond elevations to adjacent topography with ground surface elevations
lower than the ash basin full pond elevation. HDR staff performed site observations within these
identified areas as part of NPDES inspections during the reapplication process during July 2014
and documented locations where seepage was apparent at the time of the site visit. These
seeps are identified as required by GS 130A-309.210(a)(2)(ii) on Figure 2.
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Duke Energy Carolinas, LLC I Discharge Assessment Plan ���
Dan River Combined Cycle Station Ash Basin
SECTION 3 - DISCHARGE ASSESSMENT PLAN
Section 3 - Discharge Assessment Plan
3.1 Purpose of Assessment
The purpose of the assessment is to determine whether existing, known discharges from toe
drain outfalls, seeps, and weeps associated with the coal combustion residuals surface
impoundment (ash basin) have reached the surface waters of the State and have caused a
violation of surface water quality standards as required by North Carolina General Statute 130A-
J 309.210(b).
Figure 2 and Table 1 present the background and downstream sampling locations to be
considered as part of this Discharge Assessment Plan (DAP). These locations may be
assessed by comparing surface water sampling analytical results of the associated background
location with the corresponding downstream location. For discharges located at the toe of a
dam, an upstream location within the channel may not have been possible to isolate for
comparison given the proximity to the ash basin, which would have the same chemical
composition as the discharge itself. As such, the upstream location was established upstream
of the ash basin and is considered 'background." For discharges located a distance from the
ash basin, an identified upstream or "background" location for sampling may be compared to the
downstream portion of the discharge channel. The background and downstream sampling
locations are shown on Figure 2 with "B" and "D" identifiers, respectively, and the corresponding
seep locations associated with the sampling locations are indicated on Table 1.
3.2 Assessment Procedure
The assessment procedure associated with the Dan River site ash basin is provided within this
section. In addition to the specific requirements for the assessment, Section 3.2 also provides
the general requirements, the frequency of assessment, documentation requirements, and a
description of the surface water quality analyses that will be performed.
3.2.1 General Assessment Requirements
Assessments are to be performed in three phases as follows:
• Observation and Sampling (assessment site visit)
• Evaluation
• Assessment Reporting
The assessment site visit shall be performed when the background and downstream locations
are accessible and not influenced by weather events. Locations on or adjacent to the ash basin
embankments should be performed within two months after mowing, if possible. In addition, the
assessment site visit should not be performed if the following precipitation amounts have
occurred in the respective time period preceding the planned assessment site visit:
• Precipitation of 0.1 inches or greater within 72 hours or
• Precipitation of 0.5 inches or greater within 96 hours
The assessments shall be performed under the direction of a qualified Professional Engineer or
Professional Geologist on a semi-annual basis during two nonadjacent quarters. The date of the

Duke Energy Carolinas, LLC I Discharge Assessment Plan LN"i
Dan River Combined Cycle Station Ash Basin
h' SECTION 3 - DISCHARGE ASSESSMENT PLAN
initial assessment site visit shall be selected no later than 30 days from the approval of the
Discharge Assessment Plan and should fall within one of the semi-annual timeframes.
Additional seep locations that may have been identified and documented in an Identification of
New Discharge report(s) shall be reviewed prior to performing an assessment site visit, if
available.
3.2.2 Observation and Sampling
Jurisdictional determinations regarding the extent of waters of the United States and their
relationship with identified seeps at the subject facilities will be obtained from the United States
Army Corps of Engineers (USACE). Until jurisdictional determinations are finalized by USACE,
preliminary information will be used to evaluate the seeps as described in the section below.
The initial assessment site visit should be performed to document baseline conditions of the
discharge channel, including location, extent (i.e., dimensions of affected area), and flow of
each discharge. Discharge channel background and downstream locations should be verified
using a Global Positioning System (GPS) device. Photographs should be taken from vantage
points that can be replicated during subsequent semi-annual assessments.
Initial and subsequent assessment site visits shall document a minimum of the following to
respond to the requirements in 130A-309.21 0.1 (b):
• Record the most recent ash basin water surface elevation and compare to the seep and
outfall and associated discharge location surface water elevations.
• For each discharge channel, the observer shall note the following as applicable on the
day of the assessment site visit:
o Is the discharge channel flowing at the time of the assessment site visit?
o Does the discharge channel visibly flow into a Water of the U.S. at the time of the
assessment site visit?
o How far away is the nearest Water of the U.S.?
o Document evidence that flow has or could reach a Water of the U.S. (e.g.,
description of flow, including extent and/or direction) and describe the observed
condition. Evidence that flow could or has reached a Water of the U.S. may be
indicated by an inspection of the adjacent and downstream topographic drainage
features.
o Observe and document the condition of the discharge channel and outfall of the
engineered channel or seep location with photographs. Photographs are to be
taken from similar direction and scale as photographs taken during the initial
assessment site visit.
• Record flow rate within the discharge channel, if measureable, using the following
methods:
8

Duke Energy Carolinas, LLC I Discharge Assessment Plan ���
Dan River Combined Cycle Station Ash Basin
SECTION 3 - DISCHARGE ASSESSMENT PLAN
o Timed -volumetric method: Collect a volume of water from the discharge of the PVC
pipe direct) Into an appropriately sized container. Measure volumes in mL in the
PP Y� C )�
field utilizing a graduated container. Record the amount of time (in seconds)
needed to collect the volume of water and calculate the flows (in MGD) for the
timed volume.
o A V-notch weir apparatus will be installed, if necessary, during the initial
f assessment site visit to impound seepage at locations with a defined channel.
Once the impounded seep reaches equilibrium discharge, flows will be measured
using the timed -volumetric method described above.
o Area -velocity method: Measure point velocities and water depth at a minimum of
20 stations along a transect setup perpendicular to the direction of flow using a
Swoffer® 3000 flow meter mounted to a standard United States Geologic Survey
(USGS) top -set wading rod. Utilize the average velocity and cross -sectional area
of the wetted channel to calculate flows in MGD.
• Collect water quality samples using the following methods:
o Collect background and downstream samples during a period with minimal
preceding rainfall to minimize potential effects of stormwater runoff. Sampling
procedures should prevent the entrainment of soils and sediment in water samples
that can result in analytical results not being representative of the flow. Because
Areas of Wetness (AOWs)/seeps often have poorly defined flow channels and
minimal channel depth, conventional grab samples collected directly into laboratory
containers or intermediate vessels is not possible without disturbance and
entrainment 'of soils and sediments. Further, many AOWs are contiguous with low-
lying areas subject to surface water runoff and resulting heavy sediment loading
during storm events or are near surface waters subject to flooding such that
representative samples of the AOW cannot be obtained. If the facility is unable to
obtain an AOW sample due to the dry, low flow or high flow conditions preventing
the facility from obtaining a representative sample, a "no flow" result or "excessive
flow" will be recorded.
o After collection, samples will be preserved and stored according to parameter -
specific methods and delivered to the laboratory under proper Chain -of -Custody
(COC) procedures.
o Analytical parameters for analysis include: F, As, Cd, Cu, Cr, Ni, Pb, Se, and
Hg. This list includes all parameters previously identified for seep sampling at
Duke Energy power plants for which relevant stream water quality standards are in
Place. ( P
This list is responsive to the statutory requirement for the discharge
assessment to allow determination whether discharges from toe drain outfalls,
seeps, or weeps have reached surface waters and caused a violation of surface
water quality standards.) Analyses shall be conducted by Duke Energy's
Huntersville analytical laboratory (NC Wastewater Certification #248) and Pace

Duke Energy Carolinas, LLC I Discharge Assessment Plan �1J�
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SECTION 3 - DISCHARGE ASSESSMENT PLAN
Analytical Laboratories (NC Wastewater Certification # 12). Laboratory analytical
methods used for each constituent are provided in Table 2.
o Seep in -situ measurements: In -situ field parameters (temperature and pH) shall be
measured utilizing calibrated field meters either at the discharge of the seep
directly, at the discharge of the flow measurement devices, or in the water pool
created behind the device, if sufficient water depth did not exist at the device
discharge.
o Dan River and Ash Basin Sample Collection Method: Water quality samples and
in -situ measurements from the Dan River shall be collected at a location upstream
and downstream of the ash basin. Additionally, water samples and in -situ
measurements shall be collected from an in -process ash basin location. The grab
samples shall be collected from the river and basin's surface (0.3 m) directly into
appropriate sample bottles.
• In addition to sampling conducted with the semi-annual assessments, additional seep
j sampling will be conducted at locations and at a frequency as determined through
discussions with NC DEQ personnel.
3.2.3 Evaluation
Evaluation of the data from the initial assessment site visit will establish baseline conditions and
will serve as the basis for comparison for subsequent assessment site visit results. Evaluation of
observations and sampling results shall include location, extent (i.e., dimensions of affected
area), and flow of each discharge. The analytical results of the upstream and downstream
locations shall be compared to the 15A NCAC 2B standards for surface water quality upon
receipt to identify potential exceedances.
3.2.4 Assessment Reporting
Each assessment site visit shall be documented by the individual performing the assessment as
described in Section 3.2.2 to meet the requirements in 130A-309.21 0.1 (b). The report should
contain site background, observation and sampling methodology, and a summary of the
observations and descriptions of the discharge channels observed, changes in observations
compared to previous assessment events, estimates of flows quantities, and photographs of
discharges and outfalls of engineered channels designed or improved for collecting water from
the impoundment. Photographs are to be numbered and captioned. The flow and analytical
results shall be recorded and presented in tables similar to the examples provided as Tables 1
and 3. The analytical results shall be compared to the 15A NCAC 2B standards for surface
water quality and exceedances highlighted. This information shall be compiled, reviewed, and
submitted to NC DEQ within 90 days from the Observation and Sampling event.
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Dan River Combined Cycle Station Ash Basin J
SECTION 4 - REFERENCES
i
Section 4 - References
Carpenter, P. A., III. 1982. Geologic map of Region G, North Carolina: North Carolina
Department of Natural Resources and Community Development, Geological Survey
Section, Regional Geology Series 2, Scale 1:125,000.
Heath, R.C. 1984. "Ground -water regions of the United States." U.S. Geological Survey Water -
Supply Paper 2242, 78 p.
LeGrand, H.E. 1988. Region 21, Piedmont and Blue Ridge. In Hydrogeology, The Geology of
North America, vol. 0-2, ed. W.B. Back, J.S. Rosenshein, and P.R. Seaber, 201-207.
Geological Society of America. Boulder CO: Geological Society of America.
LeGrand, Harry, Sr. 2004. A Master Conceptual Model for Hydrogeological Site
Characterization in the Piedmont and Mountain Region of North Carolina, North Carolina
Department of Environment and Natural Resources.
North Carolina Department of Environment and Natural Resources, 2007. Dam Operation,
Maintenance, and Inspection Manual, North Carolina Department of Environment and
Natural Resources, Division of Land Resources, Land Quality Division, 1985 (Revised
2007).
1�
�_ 11
�i

FIGURES
"i�
TABLES
j

DATE
SITE LOCATION MAP SEPTEMBER 30, 2014
DAN RIVER COMBINED CYCLE STATION ASH BASIN
F)l DUKE ENERGY CAROLINAS, LLC FIGURE
ROCKINGHAM COUNTY, NORTH CAROLINA 1

NOTES:
1. PARCEL DATA FOR THE SITE WAS OBTAINED FROM DUKE ENERGY REAL ESTATE AND IS APPROXIMATE.
2. ASH BASIN WASTE BOUNDARY AND ASH STORAGE AREA BOUNDARIES ARE APPROXIMATE. SCALE (FEET)
3. AS -BUILT MONITORING WELL LOCATIONS PROVIDED BY DUKE ENERGY. 300, 0 300' 600,
4. ORTHOPHOTOGRAPHY WAS PROVIDED BY DUKE ENERGY (DATED 2014).
5. TOPOGRAPHIC CONTOURS WERE OBTAINED FROM NCDOT WEB SITE (DATED 2010) AND ARE APPROXIMATE. i, = 600,
6. THE ASH BASIN COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO THE DEFINITION FOUND IN 15A NCAC 02L.0107 (a.)
7. HYDROGRAPHY WAS OBTAINED FROM THE USGS NATIONAL MAP VIEWER AND DOWNLOAD PLATFORM ON JULY 8, 2014 (http://nationalmap.gov/viewer.htmi)
8. SEEP SAMPLING LOCATIONS ARE APPROXIMATE.
9. NPDES OUTFALL AND WATER QUALITY SAMPLE LOCATIONS PROVIDED BY DUKE ENERGY.
FEZ
IDENTIFIED SEEPS AND WATER QUALITY
SAMPLE LOCATION MAP
DUKE ENERGY CAROLINAS, LAC
DAN RIVER COMBINED CYCLE STATION ASH BASIN
NPDES PERMIT #NC0003468
ROCKINGHAM COUNTY, NORTH CAROLINA
DATE
DECEMBER 2014
FIGURE
2

Table 1 — Dan River Combined Cycle Station Ash Basin — Seep and Associated Discharge Locations and Descriptions
Discharge Location
See /
p
Location Coordinates
(NAD 83),
Flow
Flow Measurement
Background
Discharge Location and Discharge Sampling
Coordinates
'
Discharge
Description
(MGD) and Method
Location
Location
(NAD 83)
'ID
Latitude
Longitude
Latitude
Longitude
0.0015
West bank of Railroad Branch seeping directly into
S-1
36.493
-79.711
Continuous
timed -volumetric
stream
1-B
1-D
S-2
36.493
79.711
Continuous
0.0002
East of the Secondary Cell along natural gas line
timed -volumetric
1-D
36.492
-79.710
S 3
36.493
79.711
Continuous
0.0009
East of the Secondary Cell along natural gas line
timed -volumetric
1-D
0.0012
2-B
Southwest end of the Primary Cell
S-4
36.486
-79.719
Continuous
timed -volumetric
1-D
Notes:
1. Flow description for each seep sample location is based on observation during site visits performed by HDR in June and July 2014
2. Flow measurements and analytical samples were collected on July 7 and 14, 2014
3. Location coordinates for seep sampling locations are approximate
4. Location coordinates (degrees) in NAD 83 datum

Table 2 — Laboratory Analytical Methods
Parameter
Method
„-' Reporting
Liinit
Units '
Laboratory
Fluoride (F)
EPA 300.0
1
mg/I
Duke Energy
Mercury (Hg)
EPA 245.1
0.05
Ng/I
Duke Energy
Arsenic (As)
EPA 200.8
1
Ng/I
Duke Energy
Cadmium (Cd)
EPA 200.8
1
Ng/I
Duke Energy
Chromium (Cr)
EPA 200.8
1
Ng/I
Duke Energy
Copper (Cu)
EPA 200.8
1
Ng/I
Duke Energy
Lead (Pb)
EPA 200.8
1
Ng/I
Duke Energy
Nickel (Ni)
EPA 200.8
1
Ng/I
Duke Energy
Selenium (Se)
EPA 200.8
1
Ng/I
Duke Energy

Table 3 - Dan River Combined Cycle Station - Example Surface Water/Seep Monitoring Flow and Analysis Results Table
Parameter.
Units
S-1 '
S-2
S-3
S-4
Dan River-
Upstream
Dan River -
Downstream
Fluoride
mg/l
< 1
< 1
< 1
< 1
< 1
< 1
Hg - Mercury (71900)
Ng/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
As - Arsenic (01002)
pg/l
7.21
8.24
3.1
154
< 1
< 1
Cd - Cadmium (01027)
Ng/I
< 1
< 1
< 1
< 1
< 1
< 1
Cr - Chromium (01034)
Ng/I
2.47
2.1
2.85
< 1
1.5
1.62
Cu - Copper (01042)
Ngll
2.24
5.57
7.08
< 1
1.7
1.46
Pb - Lead (01051)
Ng/l
3.24
2.57
2.37
< 1
< 1
< 1
Ni - Nickel (01067)
Ng/l
2.66
2.31
2.93
1.36
< 1
< 1
Se - Selenium (01147)
Ng/l
< 1
< 1
< 1
< 1
< 1
< 1
pH
s.u.
6.27
7.26
6.17
7.38
6.56
6.53
Temperature
°C
18.2
20.7
19.8
24
23.9
24.6
Flow
MGD
0.0015
0.0002
0.0009
0.0012
405
405
Notes:
1. Flow measurements and analytical samples were collected on July 7 and 14, 2014
2. Flow at locations upstream and downstream of DRSS in the Dan River is the summation of USGS Dan River -Wentworth and USGS Smith River -Eden daily
average flows for the date of river sampling