8505_DukeBelewsCreek_FGD_GWAssessmentWorkplan_DIN26695_20160826

Belews Creek Steam Station 3195 Pine Hall Road Belews Creek, NC 27009
336-445-0610
336-669-2994

www.duke-energy.com Page 1 of 1
August 26, 2016

North Carolina Department of Environmental Quality Division of Waste Management
Solid Waste Section
1646 Mail Service Center
Raleigh, North Carolina 28778
Attn: Ms. Elizabeth Werner
Re: FGD Residue Landfill Proposed Work Plan
Additional Assessment of Groundwater Exceedances
Permit No.: 8505-INDUS-, Belews Creek FGD Residue Landfill
Belews Creek Steam Station Stokes County
Belews Creek, North Carolina 27009

Dear Ms. Werner,
Attached you will find the Proposed Work Plan for the Belews Creek Flue Gas Desulfurization
Residue Landfill Additional Assessment of Groundwater Exceedances. This proposed
assessment work plan is submitted as part of ongoing assessment initiated in response to your
letter dated November 9, 2011 to Mr. Ed Sullivan, P.E. (Duke Energy).
If there are any questions regarding this request, please contact me at [phone].

Respectfully submitted,
Melonie Martin
Environmental Services Attachments: Proposed Work Plan, The Belews Creek Steam Station Flue Gas Desulfurization
Residue Landfill, Permit No. 8505, Additional Assessment of Groundwater Exceedances

cc (via e-mail): Ed Mussler, NCDEQ
Shawn McKee, NCDEQ Evan Andrews, Duke Energy
Will Harrison, Duke Energy
Kimberlee Witt, Duke Energy
Ed Sullivan, Duke Energy

Proposed Work
Plan
The Belews Creek Steam Station
Flue Gas Desulfurization Residue Landfill
Permit No. 8505
Additional Assessment of Groundwater
Exceedances
Stokes County, North Carolina
August 2016

Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Contents
Table of Contents

Table of Contents ......................................................................................................................... i
Section 1 – Introduction ............................................................................................................. 1
1.1 2011 Requirement for Groundwater Assessment ......................................................... 1
1.2 Monitoring Well BC-25 Assessment ............................................................................. 2
1.3 Supplemental Groundwater Assessment ..................................................................... 3
1.4 Additional Groundwater Assessment ........................................................................... 4
Section 2 – Site Description and Groundwater Monitoring Program ........................................... 6
2.1 Site and FGD Residue Landfill Description .................................................................. 6
2.2 Site Geology and Hydrogeology ................................................................................... 7
2.3 Description of Monitoring System ................................................................................. 8
2.4 Site Groundwater Flow ................................................................................................ 8
2.5 Groundwater Quality Monitoring................................................................................... 9
Section 3 – Proposed Additional Groundwater Assessment Work Plan ....................................10
3.1 Phase I Assessment Tasks .........................................................................................10
3.2 Proposed Schedule for Assessment ...........................................................................14

Table 1: BCSS FGD Residue Landfill Groundwater Monitoring System
Table 2: BCSS FGD Reside Landfill Proposed Schedule for Assessment

Figure 1: Site Location Map
Figure 2: Site Layout
Figure 3: Proposed Additional Assessment Phase I Monitoring Well and Sample Locations

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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 1 - Introduction

Section 1 – Introduction
The Belews Creek Steam Station (BCSS) Flue Gas Desulfurization (FGD) Residue Landfill
(FGD Residue Landfill), Permit No. 8505, is located at the Belews Creek Steam Station in
Stokes County, North Carolina (Figure 1), and is owned and operated by Duke Energy
Carolinas, LLC (Duke Energy).
Exceedances of groundwater quality standards, as found in Title 15A North Carolina
Administrative Code (NCAC) Subchapter 2L .0202 Groundwater Quality Standards (2L
Standards), were reported in samples collected from groundwater monitoring well BC-25 and
other monitoring wells beginning during the May 16, 2011 sampling event. As described below,
an initial assessment and a supplemental assessment, dated October 5, 2012 and June 4,
2014, respectively, were performed to evaluate if the source of the exceedances was related to
naturally occurring conditions or to impacts from the BCSS FGD Residue Landfill.
This Phase I proposed work plan was developed to review existing data and to collect field data
to evaluate if the BCSS FGD Residue Landfill is the source of sulfate and total dissolved solids
(TDS) exceedances of the 2L Standards in monitoring wells BC-25 and BC-32 or if the adjacent
gypsum stack-out area may be the source.
1.1 2011 Requirement for Groundwater Assessment
In a letter dated November 9, 2011,1 to Mr. Ed Sullivan, P.E., of Duke Energy, the North
Carolina Department of Environment and Natural Resources (NCDENR) Division of Waste
Management (DWM) stated that exceedances of groundwater standards established in Title
15A North Carolina Administrative Code (NCAC) Subchapter 2L .0202 Groundwater Quality
Standards (2L Standards) were reported in samples collected from groundwater monitoring well
BC-25 during the May 16, 2011 sampling event.2
The NCDENR letter stated that iron was reported at a concentration greater than the respective
2L Standard in the groundwater sample collected from BC-25 during this event. Monitoring well
BC-25 is located beyond the compliance boundary. NCDENR also stated that industrial landfills
are required to comply with the 2L Standards at the compliance boundary in accordance with
15A NCAC 13B .0503 (2)(d)(iv).
In addition, the NCDENR letter stated that iron and manganese were reported at concentrations
above their respective 2L Standards in groundwater monitoring wells BC-20, BC-21, BC-23A,
BC-26, BC-27, BC-29, and BC-31. These groundwater monitoring wells are located at or
beyond the review boundary (Figure 2).
1 North Carolina Department of Environment and Natural Resources. Division of Waste Management.
November 9, 2011, Monitoring Well BC-25 Assessment. Duke Energy – Belews Creek FGD Landfill. DOC ID 15487. 2 The NCDENR letter references the monitoring event as occurring on May 6, 2011. The actual date for the sampling event was May 16, 2011.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 1 - Introduction

NCDENR stated that based on these exceedances, Duke Energy must submit a groundwater
assessment work plan to the DWM. The assessment work plan, dated February 9, 2012, was
prepared by Altamont Environmental Inc. (Altamont) on behalf of Duke Energy and was
approved by the DWM on March 23, 2012 (DOC ID 16351).
1.2 Monitoring Well BC-25 Assessment
Monitoring well BC-25 is located outside of the compliance boundary and was installed as part
of the initial permitting site investigation to obtain groundwater elevations and was subsequently
incorporated into the groundwater sampling program. It was installed on February 21, 2006,
which was more than a year prior to the pre-placement sampling at the BCSS FGD Residue
Landfill. Initial installation included a 4-inch square protective steel casing that stood 2 feet
above ground, but was later replaced with a flush mount cover. During the May 2010 sampling
event, the sampling technician found the well lid missing and mud covering the area. A new 8-
inch diameter iron pipe casing was installed around the remnant of the stick-up cover. The new
flush-mounted casing extended 8 inches above ground and was grouted within a 2-ft square
concrete pad. For protection of the well, three steel and concrete bollards were installed after
rehabilitation of the protective casing.
HDR prepared and submitted an assessment3 to NCDENR on behalf of Duke Energy for
groundwater exceedances at groundwater monitoring wells BC-20, BC-21, BC-23A, BC-25, BC-
26, BC-27, BC-29, and BC-31 and at surface water sample location SW-1.
The assessment report concluded:
• The source of iron exceedances reported in monitoring wells BC-20, BC-21, BC-23A, BC-
26, BC-27, BC-29, and BC-31 appeared to be related to turbidity introduced from naturally
occurring sources;
• The source of manganese exceedances reported in monitoring well BC-27 appeared to be
related to turbidity introduced from naturally occurring sources;
• The manganese results at monitoring well BC-21 did not appear to be related to turbidity;
and
• The iron and manganese exceedances at surface water sampling location SW-1 appeared
to be from naturally occurring sources and not related to impacts from the FGD Residue
Landfill.
The report included an assessment of 2L Standard exceedances for iron, sulfate, and TDS at
monitoring well BC-25. The iron exceedances were determined to be attributed to turbidity in
the groundwater samples and naturally occurring conditions. The assessment report concluded
that the source of the sulfate in monitoring well BC-25 appeared to be from the FGD Residue
Landfill.
HDR recommended installing an additional monitoring well at the review boundary between
monitoring well BC-25 and the FGD Residue Landfill to further delineate the sulfate and TDS
3 HDR Engineering, Inc. of the Carolinas report Groundwater Assessment, Belews Creek Steam Station, FGD Residue Landfill, Permit No. 8505, dated October 5, 2012.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 1 - Introduction

concentrations in this area and improve the understanding of groundwater flow near monitoring
well BC-25. HDR further recommended that monitoring well BC-21 be re-sampled when the
new monitoring well is sampled.
In a letter dated November 28, 2012, to Mr. Ed Sullivan, P.E., of Duke Energy, the NCDENR
Solid Waste Section approved the recommendations presented in HDR’s groundwater
assessment report dated October 5, 2012.4
1.3 Supplemental Groundwater Assessment
A supplemental groundwater assessment at the FGD Residue Landfill was performed as stated
in the recommendations in the groundwater assessment report dated October 5, 2012. The
supplemental assessment report5 dated June 4, 2014, included a description of the additional
monitoring well (BC-32) installed at the review boundary between monitoring well BC-25 and the
FGD Residue Landfill to further delineate the sulfate and TDS concentrations in this area and
improve the understanding of groundwater flow near monitoring well BC-25.
HDR reviewed the operations of the FGD Residue Landfill, the groundwater flow in the FGD
Residue Landfill area, and the analytical results for groundwater monitoring wells, and evaluated
the following as the possible sources of the exceedances for sulfate and TDS in monitoring
wells BC-20, BC-21, BC-25, and BC-32 and for selenium in monitoring well BC-21:
• Leachate leakage through the engineered liner system
• Gypsum deposited onto the ground surface infiltrating into groundwater
If the source of the sulfate and TDS in monitoring wells BC-20, BC-21, and BC-25 and the
source of the selenium in monitoring well BC-21 was caused by leakage in the liner system as a
result of the failure of the geo-synthetic clay liner (GCL) to seal a defect or damage to the
geomembrane, it was reasonable to expect that:
• The concentration of sulfate, TDS, and selenium in newly installed monitoring well BC-32
would be greater than the concentrations observed in monitoring well BC-25.
• The concentrations of sulfate and TDS in monitoring wells BC-20, BC-21, and BC-25 and
the concentration of selenium in monitoring well BC-21 would continue to increase or remain
elevated.
It was concluded in the additional assessment report that although it was not possible to
eliminate leakage through the liner system as a cause, HDR did not consider leakage through
the liner system to be the likely source of the exceedances because:
• The sulfate and TDS concentrations had decreased since May 2013 in monitoring wells BC-
20, BC-21, and BC-25, and since August 2013 in monitoring well BC-21.
4 North Carolina Department of Environment and Natural Resources, Division of Waste Management.
November 28, 2012, Groundwater Assessment Report Response. Duke Energy – Belews Creek FGD Landfill, DOC ID 17761. 5 North Carolina Department of Environment and Natural Resources, Division of Waste Management. June 4, 2014, Supplemental Groundwater Assessment. Duke Energy – Belews Creek FGD Landfill.
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• The sulfate concentrations measured in monitoring well BC-32 were less than those
measured in monitoring well BC-25.
• The selenium concentrations decreased in monitoring well BC-21 and in BC-25.
Corresponding increases and subsequent decreases in groundwater elevations compared with
sulfate and TDS concentrations were observed in monitoring wells BC-20, BC-21, and BC-25
and in selenium concentrations in monitoring well BC-21. These wells are located adjacent to
non-contact stormwater basins SB-6 and SB-7.
The additional assessment report concluded that increases in precipitation runoff received by
non-contact stormwater basins SB-6 and SB-7, due to the progress of filling Cell 1, may have
caused deposited FGD residue to be subjected to increased infiltration into the groundwater at
these basins.
Sulfate is a major component of gypsum, it is moderately soluble, and it is not likely strongly
attenuated by site soils. Based on the correlation between groundwater level and increase in
sulfate, TDS, and selenium concentrations observed in the monitoring wells located in close
proximity to the sediment basins, it appears that an increase in surface runoff and infiltration of
gypsum into the groundwater in this area may be the source of exceedances of sulfate, TDS,
and selenium in these wells.
As part of the supplemental assessment report, HDR recommended:
• Concentrations of sulfate in BC-32 are in excess of the 2L Standard. Monitoring well BC-32
was installed at the review boundary and should continue to be sampled as part of the
groundwater monitoring program for the FGD Residue Landfill.
• Although decreasing, concentrations of sulfate and TDS in BC-25 are in excess of the
respective 2L Standards. If the concentrations of sulfate and TDS decrease to below the 2L
Standard in monitoring wells BC-25 and BC-32 and remain below the 2L Standard for a
minimum of two sampling events, HDR recommends that groundwater monitoring be
discontinued in monitoring well BC-25 and that monitoring well BC-32 be incorporated into
the groundwater monitoring program for the FGD Residue Landfill as BC-32 is located at the
review boundary and BC-25 is outside of the compliance boundary. Monitoring well BC-25
would be abandoned at that time.
• If the concentrations of sulfate and TDS remain above the 2L Standards in monitoring wells
BC-25 and BC-32 for the next three sampling events, an additional assessment should be
conducted identify the source of the exceedances.
1.4 Additional Groundwater Assessment
An additional groundwater assessment will be performed based on the recommendations
presented in the June 4, 2014 supplemental groundwater assessment report and the following:
• Monitoring well BC-32 has continued to be sampled as part of the groundwater monitoring
program for the FGD Residue Landfill. This monitoring well has been sampled a total of
seven times since it was installed in August 2013.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 1 - Introduction

• Concentrations of sulfate and TDS in BC-25 were reported to be decreasing during the
supplemental assessment, but remaining in excess of the respective 2L Standards. It was
recommended that if the concentrations of sulfate and TDS decrease to below the 2L
Standard in monitoring wells BC-25 and BC-32 and remain below the 2L Standard for a
minimum of two sampling events, that groundwater monitoring be discontinued in monitoring
well BC-25 and that monitoring well BC-32 be incorporated into the groundwater monitoring
program for the FGD Residue Landfill.
• Five sampling events (May 2014, November 2014, May 2015, November 2015, and May
2016) have occurred since the supplemental groundwater assessment report was
submitted.

• Sulfate and TDS concentrations in BC-25 have generally increased during the last five
sampling events with the greatest sulfate concentration over the period of monitoring
reported during the May 2015 sampling event, and the greatest TDS concentration over the
period of monitoring reported during the November 2015 sampling event. The May 2016
analytical results for BC-25 reported concentrations for sulfate at 999,000 µg/L and TDS
concentrations at 1,560,000 µg/L.

• The sulfate and TDS concentrations reported in monitoring well BC-32 have generally
increased since the well was installed in August 2013 with the greatest concentrations over
the period of monitoring reported for both sulfate and TDS during the May 2016 sampling
event at 949,000 µg/L for sulfate and 1,380,000 µg/L for TDS. Based on the sulfate and
TDS analytical results in these wells, the groundwater monitoring in well BC-25 has not
been discontinued.
• The concentrations of sulfate and TDS have remained greater than the 2L Standards in
monitoring wells BC-25 and BC-32 during the sampling events conducted since the June 4,
2014 supplemental groundwater assessment report.
Based on these analytical results, an additional groundwater assessment will be conducted to
identify the source of the exceedances.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 2 – Site Description and Groundwater Monitoring Program

Section 2 – Site Description and Groundwater
Monitoring Program
2.1 Site and FGD Residue Landfill Description
The FGD Residue Landfill is located at Duke Energy’s Belews Creek Steam Station. Belews
Creek Steam Station is a two-unit, coal-fired generating facility located on Belews Lake in
Stokes County, North Carolina.
The FGD Residue Landfill is permitted under the NCDENR Solid Waste Permit No. 8505. The
FGD Residue Landfill is permitted to receive coal combustion products, flue gas
desulphurization residue (gypsum), wastewater treatment clarifier sludge, waste limestone
material, sand blast material, and waste coal produced at the Belews Creek Steam Station.
However, the FGD Residual Landfill typically receives only gypsum. Other waste streams are
disposed in the Craig Road Ash Landfill (Permit #8504). The FGD Residue Landfill is located
south of the Belews Creek power plant, on a peninsula of land in Belews Lake. The FGD
Residue Landfill and nearby surrounding area are depicted on Figure 1.
The location of the FGD Residue Landfill is on the northwestern facing side of a ridge running
the length of the peninsula. A gravel road, located near monitoring wells BC-28 and BC-23A,
runs generally along the crest of this ridge. Craig Road is located to the southwest of the FGD
Residue Landfill. A gypsum stack-out yard and limestone storage yard are located to the north
of the FGD Residue Landfill. A surface water drainage feature is located to the south of the
FGD Residue Landfill, draining from the topographic high east of the landfill, to the west towards
Craig Road. In general, the original site topography slopes from the ridge to the north and to
the west. Two sets of high voltage transmission lines running roughly east to west are located
immediately adjacent to and along the northern side of the FGD Residue Landfill.
The FGD Residue Landfill consists of four cells contained in an area of approximately 24 acres,
as shown on Figure 2. The landfill has an engineered liner system consisting of a leachate
collection system, underlain by a high-density polyethylene (HDPE) geomembrane liner,
underlain by a GCL. A stormwater basin is located on the western edge of the FGD Residue
Landfill and occupies an area of approximately 2.4 acres. The stormwater basin is used to
manage leachate and contact stormwater collected from the FGD Residue Landfill.
The stormwater basin is constructed with a concrete bottom surface, underlain by an HDPE
geomembrane liner, which is underlain by a GCL placed above the prepared soil foundation.
The FGD Residue Landfill first accepted waste in April 2008. Initial waste placement began in
Cell 1. As of June 30, 2013, approximately 1,078,464 tons of waste had been placed in the
landfill. Waste placement has progressed across the four cells of the landfill. As described in
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 2 – Site Description and Groundwater Monitoring Program

the operations plan, a 12-inch-thick interim soil cover layer is placed as a dust control measure
where final waste grades are achieved.6
2.2 Site Geology and Hydrogeology
In 2005, S&ME, Inc. (S&ME) prepared a site suitability study for the BCSS FGD Residue
Landfill.7 In 2015, HDR prepared a comprehensive site assessment (CSA) of the BCSS site.8
The 2005 and 2015 studies serve as the background for the discussion of the site geology and
hydrogeology. The BCSS site is located in the Milton terrane. Rock units mapped in the vicinity
of the site include alluvium, terrace deposits, sedimentary rocks of the Dan River Basin, a
diabase dike, and felsic gneisses and schists with interlayered hornblende gneiss and schist.
The alluvium consists of unconsolidated sand, silt, and clay with occasional subhedral to well-
rounded pebbles and cobles. The terrace deposits consist of unconsolidated sand, silt, and clay
with pebbles and cobles of quartz. In places, the terrace deposits are comprised of large
angular quartz fragments in a red matrix of sand, silt, and clay. The diabase occurs in a long,
relatively thin dike. The rocks of the Milton terrane in the area include interlayered augen gneiss,
quartz-feldspar gneiss, flaser gneiss, “button” mica schist, and with interlayers of hornblende
gneiss and schist.
Based on the 2005 site suitability study, the bedrock in the vicinity of the FGD Residue Landfill
generally consists of schist and gneiss. The soils that overlie the bedrock in the area have
generally formed from the in-place weathering of the parent bedrock. These soils are termed
residuum (residual soils) and saprolite. Based on the CSA site investigation, the groundwater
system in the natural materials (alluvium, soil, soil/saprolite, and bedrock) at the BCSS site is
consistent with the regolith-fractured rock system and is generally an unconfined, connected
aquifer system without confining layers. The groundwater system at the BCSS site is divided
into three layers referred to in this report as the shallow, deep (TZ), and bedrock flow layers, so
as to distinguish flow layers within the connected aquifer system.
Groundwater flow and transport at the BCSS site are assumed to follow the local slope aquifer
system. Under natural conditions, the general direction of groundwater flow can be
approximated from the surface topography. Topographic divides are located to the south and
east of the ash basin approximately along Pine Hall Road. A topographic divide exists to the
west of the ash basin along Middleton Loop Road. Another topographic divide exists north of the
ash basin along a ridgeline that extends from the east dike abutment toward the northeast.
These topographic divides generally function as groundwater divides although groundwater flow
across topographic divides may be possible based on driving head conditions from the ash
basin and the existence of preferential flow paths within the shallow and/or deep flow layers.
The predominant direction of groundwater flows north and northwest toward the Dan River.
6 Belews Creek Steam Station FGD Residue Landfill Operations Plan, prepared by Joyce Engineering, May 23, 2012, JEI Project:845.1202.11 Task 01, DIN 16987. 7 Geologic and Hydrogeologic Siting Report FGD Scrubber Residue Disposal Site Belews Creek Steam Station, Belews Creek, North Carolina, S&ME Project No. 1054-04-955, September 28, 2005. 8 Comprehensive Site Assessment Report, Belews Creek Steam Station Ash Basin, Belews Creek, North Carolina, HDR Engineering, Inc. of the Carolinas, September 9, 2015.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 2 – Site Description and Groundwater Monitoring Program

2.3 Description of Monitoring System
According to the Water Quality Monitoring Plan (WQMP),9 the groundwater monitoring system
at the FGD Residue Landfill consists of the following sampling locations, as listed in Table 1.
Table 1 - BCSS FGD Residue Landfill Groundwater Monitoring System
Monitoring Wells:
BC-7 BC-26
BC-20 BC-27
BC-21 BC-28
BC-22 BC-29
BC-23A BC-30
BC-25 BC-31
Surface Water Sample Location: SW-1
Leachate Sample: Leachate

The groundwater monitoring, surface water monitoring, and leachate sample locations are
shown on Figure 2. According to the WQMP, monitoring wells BC-23A and BC-28 represent
background groundwater quality.
Monitoring well BC-7 is used for water level measurements only. Other BCSS FGD Residue
Landfill monitoring wells are used to monitor groundwater quality in the residual soil/saprolite
layer and to measure groundwater levels.
Sampling location SW-1 is a groundwater seep located east of monitoring well BC-28. When
water is present, it emanates from the ground just above this sampling location. Therefore,
analytical results from sampling location SW-1 are compared to 2L Standards. This surface
water feature drains to Belews Lake.
The FGD Residue Landfill leachate is sampled at a location within the stormwater basin, as
shown on Figure 2.
2.4 Site Groundwater Flow
As previously described, the FGD Residue Landfill is located on the north-western side of a
ridge running the length of a peninsula between the West Belews Creek arm and the East
Belews Creek arm of Belews Lake. A gravel road, located near monitoring wells BC-28 and
BC-23A, runs generally along the crest of this ridge. Craig Road is located to the southwest of
the FGD Residue Landfill. The approximate ground elevation at monitoring well BC-28 is 815.6
feet and the approximate ground elevation at monitoring well BC-23A is 861.3 feet.
9 Water Quality Monitoring Plan FGD Scrubber Residue Landfill Belews Creek Steam Station, S&ME Project 1054-04-955, December 07, 2007.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 2 – Site Description and Groundwater Monitoring Program

The gypsum stack-out yard and limestone storage yard are located north of the FGD Residue
Landfill and monitoring wells BC-25, BC-20, and BC-21. The approximate ground elevation at
monitoring well BC-25 is 746 feet. A surface water drainage feature is located south of the FGD
Residue Landfill and drains to the west towards Craig Road. In general, the original site
topography slopes from the ridge near monitoring wells BC-28 and BC-23A towards the north
and the west. The elevation of Belews Lake ranges from approximately 722 feet to 725 feet.
The predominant groundwater discharge areas in the region of the FGD Residue Landfill are
expected to be Belews Lake to the northwest of the landfill. Generalized groundwater surface
contours from the November 2015 sampling event are shown on Figure 3.
2.5 Groundwater Quality Monitoring
In accordance with the WQMP, groundwater monitoring is performed semi-annually in May and
November. Sampling results are submitted to NCDEQ within 90 days of sampling.
The initial groundwater sampling event at the FGD Residue Landfill was performed on
November 5, 2007, prior to initial waste placement in April 2008. All 12 monitoring wells were
installed prior to the initial sampling event. Surface water sample location SW-1 was first
sampled in November 2010. The most recent groundwater monitoring event was conducted on
May 4, 2016.10
10 These results will be presented in a subsequent semiannual groundwater monitoring report due to
NCDEQ on August 2, 2016. The most recent semiannual groundwater monitoring report to have been submitted to NCDEQ was for the November 2015 monitoring event titled Semiannual Groundwater
Monitoring Report, Belews Creek Steam Station, FGD Residue Landfill, Permit No.8505, November 2015 Sampling Event, February 2, 2016, prepared by HDR Engineering, Inc. of the Carolinas.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 3 – Proposed Additional Groundwater Assessment Work Plan

Section 3 – Proposed Additional Groundwater
Assessment Work Plan
Duke Energy proposes to perform an additional groundwater assessment at the BCSS FGD
Residue Landfill to document performance of the recommendations described in Section 1
above and to identify the source of the reported groundwater exceedances.
For the purposes of this additional groundwater assessment, 2L Standard exceedances of
sulfate and TDS in monitoring wells BC-20, BC-21, BC-25, and BC-32 will be evaluated. During
the August 19, 2013 sampling event, a 2L Standard exceedance for selenium was reported in
monitoring well BC-21. An assessment of the selenium exceedance in monitoring well BC-21
was included in the June 4, 2014 supplemental groundwater assessment report.
During the May 2015 and November 2015 sampling events selenium was reported in monitoring
well BC-25 at concentrations greater than the 2L Standard. An assessment of selenium at this
monitoring well will also be included in this additional groundwater assessment report.
Sulfate and TDS concentrations reported at seep sampling location SW-1 have been generally
increasing over the period of monitoring. A preliminary review of the May 2016 sampling results
indicate a 2L Standard exceedance of sulfate at this location. An assessment of sulfate and
TDS at SW-1 will also be included in this additional groundwater assessment report.
The groundwater assessment will be performed in two phases. The initial phase, Phase I, will
be used to review existing data and to collect field data that will be used to evaluate if the BCSS
FGD Residue Landfill is the source of the exceedances. The results from Phase I will be used
to identify if any additional field efforts (ex. installation of additional groundwater monitoring
wells), is required, in Phase II to determine if the FGD Residue Landfill is the source of
exceedances.
3.1 Phase I Assessment Tasks
Task 1 - Review of Existing Data
HDR will review existing analytical, hydrogeologic data, as well as landfill construction and liner
data provided by Duke Energy.
Task 2 – Well Inspection, Cleaning and Redevelopment
The BCSS FGD Residue Landfill compliance monitoring well records will be reviewed for wells
with historically high (>10 NTU) turbidity values. HDR will also evaluate the BCSS FGD
Residue Landfill compliance wells (BC-20, BC-21, BC-22, BC-23A, BC-25, BC-26, BC-27, BC-
28, BC-29, BC-30, BC-31, and BC-32) for evidence of surficial contamination (soil, debris, etc.)
at the well heads. During the well head inspections of the compliance wells, depth to
groundwater will be gauged and recorded. Any compliance monitoring wells identified with
historical high turbidity readings and/or surficial contamination will have the well head area
cleaned of surficial debris and the wells evacuated of between 10 and 20 well volumes
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 3 – Proposed Additional Groundwater Assessment Work Plan

(redeveloped). Following well head cleaning and redevelopment, the BCSS FGD Residue
Landfill compliance well heads will be fitted with neoprene well caps to prevent any future
potential debris from entering the wells.
Task 3 – Collect and Analyze Soil and Surface Water Samples
Monitoring wells BC-25, BC-32, BC-21, and BC-20 are located between the BCSS FGD
Residue Landfill and the gypsum stack-out area, as shown on Figure 3. Soil samples will be
collected from locations between the BCSS FGD Residue Landfill and the gypsum stack-out
area to evaluate possible sources for the exceedances. Background soil samples will be
collected at similar depths from a location east of the FGD Residue Landfill (FGDBGSB-1).
Sample locations include the sediment basins north of the landfill, the ditch area adjacent to BC-
25, and other areas as shown on Figure 3. Based on the location of a surface water drainage
ditch adjacent to BC-25, the surface water drainage from the gypsum stack-out area may be
contributing to the groundwater exceedances in the area.
Soil samples will be collected using a hand auger at the following depths: ground surface, 1 foot
below ground surface (bgs), 2 feet bgs, 3 feet bgs, and at hand auger refusal depth (or 5 feet
bgs, whichever is encountered first).
The soil samples will be analyzed for the following constituents using the following methods:
• Boron, iron, and manganese using U.S. Environmental Protection Agency (EPA) Method
6010
• Selenium using EPA Method 6020
• Sulfate and fluoride using Standard Method (SM) 9056
• Chloride using SM 4500-Cl-E
If surface water is observed in the sediment basins or in the ditch near BC-25, surface water
samples will be collected from SW-1 and the four (4) other SW locations shown on Figure 3
(SW-2 through SW-5). If surface water is not identified in these locations, soil samples will be
collected with a hand auger from the depths previously described. Surface water samples will
be analyzed for the same parameters and constituents as used in the landfill groundwater
monitoring program using the same analytical methods:
• Barium, boron, chromium, copper, iron, manganese, nickel, silver, and zinc using
Environmental Protection Agency (EPA) Solid Waste (SW) 84611 - Method 6010D
• Arsenic, cadmium, lead, and selenium by EPA SW 846 - Method 6020B
• Chloride, fluoride, nitrate as nitrogen, and sulfate using EPA SW 846 - Method 9056A
• Mercury using EPA SW 846 - Method 7470A
• Total Dissolved Solids using Standard Method (SM) 2540C
11 EPA Hazardous Waste Test Methods (SW-846); available online at https://www.epa.gov/hw-sw846
(Accessed July 1, 2016)
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Laboratory analyses of soil and water samples will be performed by a NC certified laboratory.
Task 4 Install Water Level and Conductance Logger in BC-25
As noted above, a surface water drainage ditch is located adjacent to BC-25. To assist in
evaluating possible impacts from surface water, a data logger, capable of measuring and
recording water levels, temperature, and conductivity will be installed in BC-25. The logged
data will be reviewed for changes that may be attributed to infiltration of surface water. The
logger will collect data for a minimum of 60 days. For comparison to background conditions, a
second logger, will be installed to monitor the same parameters in BC-28, the site background
well. Data will be downloaded every 2 weeks over the period of monitoring to assure the
datalogger are functioning properly.
Task 5 Installation of Assessment Groundwater Monitoring Wells
If additional information is required to complete the assessment, two pair of assessment
groundwater monitoring wells are proposed to be installed along the northern side of the FGD
Residue Landfill (Figure 3). Each location will consist of a shallow “S” and a deep “D”
monitoring well (FGDLA-1S/D and FGDLA-2S/D).
The location of these monitoring wells between the existing landfill monitoring wells with
reported exceedances and the landfill limit of waste are appropriate for determining if the landfill
is the source of reported exceedances. The analytical results obtained from these monitoring
wells will be used to determine if the source of exceedances is the FGD Residue Landfill. The
water levels gauged in these monitoring wells will be used in conjunction with the existing
monitoring wells to refine the groundwater flow contours at the landfill.
Shallow “S” monitoring wells in regolith are defined as wells that are screened wholly within the
regolith zone and set to bracket the water table surface at the time of installation. At each
monitoring well location, a shallow well will be constructed with a 2-inch-diameter, schedule 40
PVC screen and casing. Each of these wells will have a 10-foot to 15-foot pre-packed well
screen having manufactured 0.010-inch slots.
Deep “D” monitoring wells are defined as wells that are screened within the partially
weathered/fractured bedrock transition zone at the base of the regolith. Generally, at each deep
monitoring well location, a double-cased well was constructed with a 6-inch-diameter PVC outer
casing and a 2-inch-diameter PVC inner casing and well screen. The purpose of installing
cased wells at the site is to prevent possible cross-contamination of flow zones within the
shallow and deeper portions of the unconfined aquifer during well installation. Outer well
casings (6-inch casing) were advanced to auger refusal and set approximately 1 foot into PWR
(if present). The annulus between the borehole and casing was grouted to the surface using the
tremie grout method. After the grout was allowed to cure for a period of 24 hours, the borehole
was extended via coring approximately 10 feet to 15 feet into transition zone rock using an HQ
core barrel. A 2-inch-diameter well with a 5-foot pre-packed well screen was set at least 2 feet
below the bottom of the outer casing.
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 3 – Proposed Additional Groundwater Assessment Work Plan

Rock cores will be logged in accordance with the Field Guide for Rock Core Logging and
Fracture Analysis by Midwest GeoSciences Group. Percent recovery and rock quality
designation (RQD) will be calculated in the field. The cores will be photographed and retained.
Newly installed monitoring wells will be developed to create an effective filter pack around the
well screen and to remove fine particles within the well from the formation near the borehole.
Based on site specific conditions per 15A NCAC 02C .0108(p), appropriate measures (e.g.,
agitation, surging, pumping, etc.) will be utilized to stress the formation around the screen and
the filter pack so that mobile fines, silts, and clays are pulled into the well and removed.
Water quality parameters (specific conductance, pH, temperature, oxidation reduction potential
(ORP), and turbidity) will be measured and recorded during development and should stabilize
before development is considered complete. Development will continue until development
water is visually clear (< 10 Nephelometric Turbidity Units (NTU) Turbidity) and sediment free as
determined by the absence of settled solids.
If a well cannot be developed to produce low turbidity (< 10 NTU) groundwater samples,
NCDEQ will be notified and supplied with the well completion and development measures that
have been employed to make a determination if the turbidity is an artifact of the geologic
materials in which the well is screened.
Following development, sounding the bottom of the well with a water level meter should indicate
a “hard” (sediment-free) bottom. Development records will be prepared under the direction of
the Project Scientist/Engineer and will include development method(s), water volume removed,
and field measurements of temperature, pH, conductivity, and turbidity.
If after review of the existing data and data from the newly installed monitoring wells it cannot be
confirmed whether the source of the reported exceedances is the landfill, additional assessment
activities will be conducted which may include the installation of additional monitoring wells.
Task 6 Phase I Assessment Report
A report will be developed to document the Phase I assessment tasks, to present the findings,
and based on this information, to present the source of the exceedances. In addition, the report
will contain potentiometric surface maps and will contain iso-concentration maps of the
analytical results related to exceedances.
The report will be submitted to NCDEQ 60 days after the completion of the Task 4 data
collection.
If the evaluation presents that the BCSS FGD Residue Landfill is the source of the
exceedances, the report will provide proposed locations and the schedule for the installation of
additional monitoring wells to delineate the extent of the groundwater exceedances, a proposed
monitoring plan, and a proposed schedule for corrective action at the BCSS FGD Residue
Landfill.
If the Phase I evaluation finds that the FGD Residue Landfill is not the source, the report will
contain recommendations for Phase II assessment including the locations and proposed
schedule for the installation of additional groundwater monitoring wells and additional sampling
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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Section 3 – Proposed Additional Groundwater Assessment Work Plan

as required to determine the source of the exceedances and to further delineate the extent of
exceedances.
3.2 Proposed Schedule for Assessment
The schedule for completion of this scope of work is contingent on NCDEQ approval of the
proposed work plan. HDR proposes the following schedule for the assessment tasks (Table 2)
relative to receipt of authorization and Notice to Proceed (NTP) by Duke Energy procurement
subsequent to NCDEQ approval of the proposed work plan.
Table 2 - BCSS FGD Reside Landfill Proposed Schedule for Assessment
Task Proposed Completion Date – after approval by NCDEQ and receipt of authorization and Notice to Proceed
Task 1 - Review of existing data 1 week
Task 2- Well Inspection, Cleaning, and Redevelopment 3 weeks
Task 3 – Collect and Analyze Soil and Surface Water Samples 3 weeks – collection of samples
7 weeks – complete laboratory analyses, review data
Task 4 - Install of Water Level and Conductance
Logger in BC-25 3 weeks – install loggers
11 weeks – record data for 60 days
Task 5 – Potential Installation of Assessment Monitoring Wells 16 weeks
Task 6 - Submit Phase I Assessment Report 24 weeks

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Duke Energy Carolinas, LLC | The Belews Creek Steam Station FGD Residue Landfill Proposed Work Plan: Delineation of Exceedances above 2L Standards Figures

Figures