Cape Fear CBE - Appendix C_20191230

Wood Environment & Infrastructure Solutions, Inc. Woo
Duke Energy Coal Combustion Residuals Management Program
d.
Cape Fear Station Basin Closure Plan
APPENDIX C — Engineering Evaluations and
Analysis
Rev. 0
December 5, 2019

wood.
March 28, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Cape Fear 1956 Ash Pond H&H Update
Summary of Supporting H&H Analyses
Duke Energy — Cape Fear Steam Station
Chatham County, North Carolina
Wood E&IS Project No. 7812-19-0142
Dear Mr. Smith,
As authorized by Duke Energy Carolinas, LLC (Duke Energy), Wood Environment & Infrastructure
Solutions, Inc. (Wood E&IS) has revised the Hydraulic and Hydrologic analysis (H&H) based upon
a full Probable Maximum Precipitation (PMP) rainfall event to determine if the ash basins located
at the Cape Fear Steam Station have sufficient capacity for the design storm with the current
outlet conditions.
Background Information
The Cape Fear Plant is located at 500 CP&L Road near Moncure, North Carolina, and is
reported to have begun commercial operation in 1923. Two of the original coal-fired generating
units were retired in 1977 and two additional units were retired in 2011. The remaining two
units, along with one of four oil -fired combustion turbine units on site, were retired in October
2012. There are five Ash Pond Areas identified by NCDENR Division of Energy, Mineral and
Land Resources, Land Quality Section, Dam Safety Program at the Cape Fear Plant. Ash
material or coal combustion residuals (CCR) has historically been deposited within the Ash
Ponds located on site by hydraulic sluicing operations for both fly ash and bottom ash material.
There are no longer any ash disposal operations with the Ash Pond areas with the permanent
retirement of the fossil generating units.
The 1956 Ash Pond is located at the northwest corner of the plant site adjacent to the Haw
River and near the confluence with the Deep River that then forms the Cape Fear River. From
Correspondence:
Wood Environment &infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodplc.com
Licensure NC Engineering F-1253 NC Geology C-247

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1956 Ash Pond H&H Update
Page 2 Wood E&IS Project No. 7812-19-0142
review of available descriptive information, this Ash Pond has a surface area of about 12 acres,
maximum dike height of about 20 feet, crest width in the range of 7-10 feet, crest level in the
range of Elevation 182-190 feet, and dike length of approximately 3,200 feet. The upstream
(interior) slope is reported to be about 2(horizontal): 1 (vertical), and the downstream (exterior)
slope is reported to be in the range of 1:1 to 1.5:1. The dike along the southeast side of the Ash
Pond was formed by the plant flood protection levee. There are no records available for design
and construction of the 1956 Ash Pond. The south portion of the 1956 Ash Pond was formed in
1954 as part of the plant flood protection levee. Historical photographs of the levee construction
show material being placed in lifts and rolled with compaction equipment. The remaining dikes
(north, east, and west) forming the ash pond were constructed in 1956 using excavated material
from within the pond area. The 1956 dikes were constructed using a crane with a drag bucket
and later shaped with bulldozers. The 1956 Ash Pond is now completely filled with sedimented
ash and is generally grown over with heavy brush and vegetation. The original outlet structures
were permanently abandoned by grouting in 2015.
The 1956 Ash Pond has remained inactive for several decades and does not currently have an
NPDES permit. The pond is regulated under the NCDENR Division of Energy, Mineral and
Land Resources, Land Quality Section, Dam Safety Program as a High Hazard Dam, and is
identified in the regulatory program as "Cape Fear 1956 Ash Pond Dam (Inactive)" (State I.D.
No. CHATH-075).
H&H Evaluation Criteria
North Carolina's Department of Environmental Quality (NCDEQ) Dam Safety has adopted the
Federal CCR Rule and per the dam safety High Hazard Classification, each ash basin is now
required to pass a full Probable Maximum Precipitation (PMP). Each basin is classified as high
hazard by NCDEQ due to the potential for environmental impacts greater than $200,000, if the
basin failed.
The computer program HydroCAD Version 10.0 was initially used to perform the H&H calculations
to determine if the current conditions (revised per updated survey information) could safely pass
or store the revised design storm (full PMP storm event) without an uncontrolled discharge.
Previously, the design storm was listed as the'/2 PMP storm event. NCDEQ has requested that
the supporting modeling information be provided in either HEC-RAS or HEC-HMS format. In
accordance with the new guidelines, the Hydrologic Engineering Center Hydrologic Modeling
System (HEC-HMS, version 4.3) computer program was used to perform the hydrologic &
hydraulic (H&H) calculations.
The existing conditions for the Ash Ponds were obtained from best available reports and
topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation Cape Fear Ash
Ponds, McKim and Creed Topographic Survey (2014), Fleming Engineering, Inc. Topographic
Surveys (2015), and LiDAR Topographic Survey by WSP (2015).
The Cape Fear Ash Ponds are classified as high hazard, with the revised regulatory design storm
for the ponds of the full PMP storm event. Based on the Hydrometeorological Report No. 51,
Probable Maximum Precipitation Estimates, United States East of the 105th Meridian, from the

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1956 Ash Pond H&H Update
Page 3 Wood E&IS Project No. 7812-19-0142
National Oceanic and Atmospheric Administration (Figure 18: All -Season PMP (in.) for 6 hr 10
mil) the PMP for the Cape Fear site is as follows:
• PMP = 29.50 inches of rainfall for 6 hours
Based on field observations and aerial imagery, each of the sub -basins within the 1956 Ash Basin
were assigned appropriate curve numbers (CN) for the general condition of land covers with an
appropriate time of concentration calculated for each area by using TR-55 recommendations.
The storage for the basin was developed assuming initial conditions having no water stored in the
basin. The storage for the basin was estimated using the prismatic volume calculation method
with the elevation -surface area input data. Storage volumes were determined from contours
derived from the existing conditions. Ponding area details can be found in the modeling results.
The H&H Analysis was conducted for the stage -storage conditions, with no outlet structure in
operation. The basin is filled with ash, and stormwater would likely infiltrate into the underlying
ash material during a storm event. However, for the purpose of this analysis, it is assumed that
no infiltration occurs. A minimum time of concentration (Tc) was calculated for the pond consistent
with T-55 methods in HydroCAD. The length of the flow paths of sheet flow, shallow concentrated
flow, and channel flow as well as slope and channel characteristics were determined based on
the topography, which is consistent with TR-55 recommendations. Additional details on time of
concentration for each pond can be found in the modeling HydroCAD results. The storage for the
basin was estimated using the prismatic volume calculation method with the elevation -surface
area input data. Storage volumes for the 1956 Ash Pond were determined from contours derived
from the grading of the Ash Pond Regrading Project associated with CF-110 (2015) as shown on
the record survey by Fleming Engineering, Inc. (2015). Additional ponding area details can be
found in the modeling results. Wood E&IS assumed a Type II storm distribution for the 6-hr peak
hydrograph.
In order to support the request by NCDEQ to model the basin in HEC-RAS/HMS format, the
existing hydraulic models created in HydroCAD were re-created using USACE HEC-RAS version
5.0 or HEC-HMS version 4.3. The HEC-RAS/HMS models were developed using inputs from the
existing HydroCAD models to the greatest extent possible. At a minimum, the following inputs
required for the development of the HEC-RAS/HMS model were utilized:
• Rainfall data, curve numbers, time of concentration for hydrologic computations
• Stage -Storage rating curves for the ash ponds
• Outlet rating curves
H&H Summary
Using the information above and the design storm hydrograph, Wood EMS completed the H&H
Analyses using HEC-HMS version 4.3 and ran the models for 360 hours (15 days) to allow
sufficient time for 80% drawdown. Results of the analyses are shown below in Table 1. The
current conditions fail for the design storm (PMP storm event) in the 1956 Ash Pond due to
overtopping of the dam crest.

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1956 Ash Pond H&H Update
Page 4 Wood E&IS Project No. 7812-19-0142
Table 1. Modeling Results — 1956 Ash Basin
Updated Results
1956 Ash Pond
Full PMP Storm Event
1956 Ash Pond
2x Full PMP Storm Event
Peak Stage during OF (ft)
186.2
186.2
Dike Elevation (ft)
186.0
186.0
Pond Freeboard (ft)
-0.2 (Overtops)
-0.2 (Overtops)
100% Inflow Volume (acre-ft)
31.9
63.7
80% Inflow Volume (acre-ft)
25.5
51.0
80% Discharge Time (hr)
N/A
N/A
According to Dam Safety 15A NCAC 2K.0205, the spillway system shall be capable of removing
at least 80 percent of the water temporarily detained above the elevation of the primary spillway
within 15 days following passage of the design storm peak. There is no spillway associated with
the 1956 Ash Basin. Thus, the ash basin is not compliant with 15A NCAC 2K.0205. The results
for these calculations are attached.
Conclusion
Based on the results of this study and considering the conservative assumption made (no
infiltration) Wood E&IS concludes the existing conditions of the 1956 Ash Basin will not safely
store or pass the design storm (full PMP storm event) without an uncontrolled discharge, nor does
the 1956 Ash Basin meet the drawdown requirements per 15A NCAC 2K 0.0205.
Closing
Wood E&IS appreciates the opportunity to offer our services on this project. If you have
any questions concerning this response, please contact us.
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
ggaEdfq9z3etiIIPIP/IPPPP
CA jy
-,SPA,
William A. Williams, PE, PG
Senior Engineer
HEC-HMS model files provided separately
Jeffery Mann, PE
Chief Engineer

wood.
March 28, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Cape Fear 1963/1970 Ash Pond H&H Update
Summary of Supporting H&H Analyses
Duke Energy — Cape Fear Steam Station
Chatham County, North Carolina
Wood E&IS Project No. 7812-19-0142
Dear Mr. Smith,
As authorized by Duke Energy Carolinas, LLC (Duke Energy), Wood Environment & Infrastructure
Solutions, Inc. (Wood E&IS) has revised the Hydraulic and Hydrologic analysis (H&H) based upon
a full Probable Maximum Precipitation (PMP) rainfall event to determine if the ash basins located
at the Cape Fear Steam Station have sufficient capacity for the design storm with the current
outlet conditions.
Background Information
The Cape Fear Plant is located at 500 CP&L Road near Moncure, North Carolina, and is reported
to have begun commercial operation in 1923. Two of the original coal-fired generating units were
retired in 1977 and two additional units were retired in 2011. The remaining two units, along with
one of four oil -fired combustion turbine units on site, were retired in October 2012. There are five
Ash Pond Areas located at the Cape Fear Plant. Ash material or coal combustion residuals (CCR)
has historically been deposited within the Ash Ponds located on site by hydraulic sluicing
operations for both fly ash and bottom ash material. There are no longer any ash disposal
operations with the Ash Pond areas with the permanent retirement of the fossil generating units.
The 1963 Ash Basin and the 1970 Ash Basin were combined into a single ash basin during the
construction of the 1970 Ash Basin. For the purpose of this report, the 1963 Ash Pond and 1970
Ash Pond will be referred to as one pond called the 1963/1970 Ash Pond.
Correspondence:
Wood Environment &Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
•
Licensure NC Engineering F-1253 NC Geology C-247

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 196311970 Ash Pond H&H Update
Page 2 Wood E&IS Project No. 7812-19-0142
The combined 1963/1970 Ash Pond is located on the southwest corner of the site adjacent to the
east bank of the Cape Fear River. The 1963/1970 Ash Pond has remained inactive for several
decades and does not currently have an NPDES permit. The pond is regulated under the
NCDENR Division of Energy, Mineral and Land Resources, Land Quality Section, Dam Safety
Program as a High Hazard Dam, and is identified in the regulatory program as "Cape Fear 1963
Ash Pond Dam (Inactive)" (State I.D. No. CHATH-076) and "Cape Fear 1970 Ash Pond Dam
(Inactive)" (State I.D. No. CHATH-077).
From review of available descriptive information, the 1963 Ash Pond has a surface area of about
21 acres, maximum dike height of about 22 feet, crest width in the range of 12-14 feet, crest level
at Elevation 197 feet, and dike length of approximately 4,000 feet. The upstream (interior) slope
is reported to be in the range of 1.5:1 to 2:1, and the downstream (exterior) slope is reported to
be 1.5:1. From review of available descriptive information, the 1970 Ash Pond has a surface area
of about 30 acres, maximum dike height of about 27 feet, crest width in the range of 12-14 feet,
crest level at Elevation 197 feet, and dike length of approximately 4,600 feet. The upstream
(interior) slope is reported to be about 2:1, and the downstream (exterior) slope is reported to be
2:1.
The original 1963 Ash Pond area was constructed with a crest level at Elevation 188 feet. The
perimeter enclosure dikes for the 1963 Ash Pond were extended and incorporated into the 1970
Ash Pond to form the current combined area. The crest level for the combined 1963/1970 Ash
Pond area is at Elevation 197 feet. The crest level for the 1963 Ash Pond area was raised from
Elevation 188 feet to Elevation 197 feet when the two Ash Pond areas were combined. The
common separating dike originating from the 1963 Ash Pond area was apparently cut down to
the allow flow to pass into the 1970 Ash Pond area. Remnants of the original separating dike
have been observed from field inspections. There are limited records available for design of the
1970 Ash Pond and no records for construction of the combined 1963/1970 Ash Pond area.
The 1963/1970 Ash Pond encompasses approximately 51 acres. There is limited documentation
for the design and construction of the 1963 Ash Pond dikes. Available information suggests the
dike had no cutoff into natural ground nor an internal drainage system. An outlet structure was
installed near the southwest corner of the pond and was removed when the 1970 Ash Pond was
constructed. There is no available documentation for the removal or abandonment of the 1963
Ash Pond outlet structure. The 1970 Ash Pond was constructed by extending the dikes south
from the original 1963 Ash Pond. The south dike of the 1963 Ash Pond area was partially
removed allowing both pond areas to use a common discharge outlet structure located at the
southwest end of the 1970 Ash Pond area. Operational utilization of the combined 1963 and
1970 Ash Pond area was stopped in 1982. The majority of the 1963/1970 Ash Pond area is filled
with sedimented ash and receives inflow only from rainfall over the pond area. Rainfall on the
pond collects in the southeast corner of the 1970 Ash Pond and is eventually released through
infiltration or the common discharge outlet structure and pipe. The combined Ash Pond area is
overgrown with heavy brush and vegetation with the exception of the ponding area.

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1963/1970 Ash Pond H&H Update
Page 3 Wood E&IS Project No. 7812-19-0142
H&H Evaluation Criteria
North Carolina's Department of Environmental Quality (NCDEQ) Dam Safety has adopted the
Federal CCR Rule and per the dam safety High Hazard Classification, each ash basin is now
required to pass a full Probable Maximum Precipitation (PMP). Each basin is classified as high
hazard by NCDEQ due to the potential for environmental impacts greater than $200,000, if the
basin failed.
The computer program HydroCAD Version 10.0 was initially used to perform the H&H calculations
to determine if the current conditions (revised per updated survey information) could safely pass
or store the revised design storm (full PMP storm event) without an uncontrolled discharge.
Previously, the design storm was listed as the'/2 PMP storm event. NCDEQ has requested that
the supporting modeling information be provided in either HEC-RAS or HEC-HMS format. In
accordance with the new guidelines, the Hydrologic Engineering Center Hydrologic Modeling
System (HEC-HMS, version 4.3) computer program was used to perform the hydrologic &
hydraulic (H&H) calculations.
The existing conditions for the Ash Pond was obtained from best available reports and
topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation Cape Fear Ash
Ponds, McKim and Creed Topographic Survey (2014), Fleming Engineering, Inc. Topographic
Survey (2015), and LiDAR Topographic Survey by WSP (2015).
The Cape Fear Ash Ponds are classified as high hazard, with the revised regulatory design storm
for the ponds of the full PMP storm event. Based on the Hydrometeorological Report No. 51,
Probable Maximum Precipitation Estimates, United States East of the 105th Meridian, from the
National Oceanic and Atmospheric Administration (Figure 18: All -Season PMP (in.) for 6 hr 10
mil) the PMP for the Cape Fear site is as follows:
• PMP = 29.50 inches of rainfall for 6 hours
Based on field observations and aerial imagery, the basin was assigned appropriate curve
numbers (CN) for the general condition of land covers with an appropriate time of concentration
calculated for each area by using TR-55 recommendations.
The storage for each basin was developed from the assumed initial water elevation to the top of
dam. The storage for each basin was estimated using the prismatic volume calculation method
with the elevation -surface area input data. Storage volumes were determined from contours
derived from the existing conditions. Additional ponding area details can be found in the modeling
results.
The H&H Analysis was conducted for the proposed stage -storage conditions and Table 1 provides
information on the current outlet structure. The H&H Analysis was conducted for the stage -
storage conditions.

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 196311970 Ash Pond H&H Update
Page 4 Wood E&IS Project No. 7812-19-0142
Table 1. 1963/1970 Ash Pond Outlet Existing Conditions
1963/1970 Ash Pond
Characteristic
Existing
Dike Crest Elevation (ft)
184.53
Culvert Diameter (in)
32
Culvert Elevation (ft)
176.91
Culvert Material
HDPE
The basins are generally filled with ash, and stormwater would likely infiltrate into the underlying
ash material during a storm event. However, for the purpose of this analysis, it is assumed that
no infiltration occurs. A water ponding area is in the southeast portion of the 1970 Ash Basin.
The minimum time of concentration (Tc) was calculated for the pond consistent with T-55 methods
in HydroCAD. The length of the flow paths of sheet flow, shallow concentrated flow, and channel
flow as well as slope and channel characteristics were determined based on the topography,
which is consistent with TR-55 recommendations. Additional details on time of concentration for
each pond can be found in the modeling HydroCAD results. The storage for each basin was
estimated using the prismatic volume calculation method with the elevation -surface area input
data. Storage volumes for the 1970 Ash Pond were determined from contours derived from the
McKim and Creed Topographic Survey (2014), Fleming Engineering, Inc. Topographic Survey
(2015), and LiDAR Topographic Survey by WSP (2015). Additional ponding area details can be
found in the modeling results. Wood E&IS assumed a Type II storm distribution for the 6-hr peak
hydrograph.
In order to support the request by NCDEQ to model the basin in HEC-HMS format, the existing
hydraulic models created in HydroCAD were re-created using HEC-HMS version 4.3. The HEC-
HMS models were developed using inputs from the existing HydroCAD models to the greatest
extent possible. At a minimum, the following inputs required for the development of the HEC-
HMS model were utilized:
• Rainfall data, curve numbers, time of concentration for hydrologic computations
• Stage -Storage rating curves for the ash ponds
• Outlet rating curves
H&H Summary
Using the information above and the design storm hydrograph, Wood E&IS completed the H&H
Analyses using HEC-HMS version 4.3 and ran the models for 360 hours (15 days) to allow
sufficient time for 80% drawdown. The results of the analyses are shown below in Table 2. The
current conditions fail for the design storm (PMP storm event) in the 1963/1970 Ash Pond due to
overtopping of the dam crest.

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 196311970 Ash Pond H&H Update
Page 5 Wood E&IS Project No. 7812-19-0142
Table 2. Modeling Results
Updated Results
1963/1970 Ash Pond
(HydroCAD Pond 1P)
Peak Stage during OF (ft)
184.7
Minimum Dike Elevation (ft)
184.0
Pond Freeboard (ft)
-0.70 (Overtops)
100% Inflow Volume (acre-ft)
84.2
80% Inflow Volume (acre-ft)
67.4
(Minimum) 80% Discharge Time (hr)
4.2
According to Dam Safety 15A NCAC 2K.0205, the spillway system shall be capable of removing
at least 80 percent of the water temporarily detained above the elevation of the primary spillway
within 15 days following passage of the design storm peak. Based upon the existing conditions,
the 1963/1970 Ash Pond does not safely store the design storm event. However, the existing
conditions release more than 80% of the inflow to the ash basin within 15 days after the design
storm begins. Thus, the current structure is compliant with 15A NCAC 2K.0205. The results for
the calculations are attached.
Conclusion
Based on the results of this study, Wood E&IS concludes the existing conditions will not safely
contain the design storm (full PMP) without an uncontrolled discharge but will meet the drawdown
requirements per 15A NCAC 2K 0.0205.
Closing
Wood E&IS appreciates the opportunity to offer our services on this project. If you have
any questions concerning this response, please contact us.
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
William A. Williams, PE, PG
Senior Engineer
HEC-HMS model files provided separately
5g4�9f t5 I D 11P111 j1P
CA
i )
A,ISS�OIt/.�13l Ls C:lti�•44
Jeffery Mann, PE
Chief Engineer

wood.
March 28, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Cape Fear 1978 Ash Pond H&H Update
Summary of Supporting H&H Analyses
Duke Energy — Cape Fear Steam Station
Chatham County, North Carolina
Wood E&IS Project No. 7812-19-0142
Dear Mr. Smith,
As authorized by Duke Energy Carolinas, LLC (Duke Energy), Wood Environment & Infrastructure
Solutions, Inc. (Wood E&IS) has revised the Hydraulic and Hydrologic analysis (H&H) based upon
a full Probable Maximum Precipitation (PMP) rainfall event to determine if the ash basins located
at the Cape Fear Steam Station have sufficient capacity for the design storm with the current
outlet conditions.
Background Information
The Cape Fear Plant is located at 500 CP&L Road near Moncure, North Carolina, and is
reported to have begun commercial operation in 1923. Two of the original coal-fired generating
units were retired in 1977 and two additional units were retired in 2011. The remaining two
units, along with one of four oil -fired combustion turbine units on site, were retired in October
2012. There are five Ash Pond Areas located at the Cape Fear Plant. Ash material or coal
combustion residuals (CCR) has historically been deposited within the Ash Ponds located on
site by hydraulic sluicing operations for both fly ash and bottom ash material. There are no
longer any ash disposal operations with the Ash Pond areas with the permanent retirement of
the fossil generating units.
The 1978 Ash Pond (CHATH-078) is located south of the Cape Fear Plant facility, positioned
east of the 1963/1970 Ash Pond, and adjacent to the Cape Fear Plant discharge canal.
Correspondence:
Wood Environment &Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
•
Licensure NC Engineering F-1253 NC Geology C-247

Duke Energy
March 28, 2019
Page 2
Cape Fear Plant
Cape Fear 1978 Ash Pond H&H Update
Wood E&IS Project No. 7812-19-0142
From review of available descriptive information, this 1978 Ash Pond has a surface area of
about 36 acres, maximum dike height of about 27 feet, crest width of 15 feet, crest level at
Elevation 197 feet, and dike length of approximately 5,600 feet. The upstream (interior) slope is
reported to be 2:1, and the downstream (exterior) slope is reported to be 2:1.
The 1978 Ash Pond was formed by incorporating a portion of the 1963/1973 Ash Pond dike on
the west side, and constructing new dikes on the north, south and east sides. Design was
reported to have been provided by CP&L with technical support from William L. Wells. Limited
records for design and construction are available for review. There are no provisions for
seepage control (internal drain or blanket) provided for the dike based on review of available
design information.
The 1978 Ash Pond operates under a National Pollutant Discharge Elimination System
(NPDES) permit number NC0003433 issued by the North Carolina Department of Environment
and Natural Resources (NCDENR) Division of Water Quality as a water treatment unit. The
basin exterior embankment is regulated by NCDENR Division of Energy, Mineral and Land
Resources, Land Quality Section, Dam Safety Program as a High Hazard Dam, and is identified
in the regulatory program as "Cape Fear 1978 Ash Pond Dam" (State I.D. No. CHATH-078).
The discharge outlet structure was formerly located in the southeast corner of the pond and
discharged into the plant discharge canal. The outlet structure was permanently abandoned in
2015, when pumping associated with treatment was initiated. The plant is no longer directing
ash to the 1978 Ash Pond area. The majority of the 1978 Ash Pond area is filled with
sedimented ash and only receives inflow from rainfall over the basin area. Rainfall on the pond
collects in the southeast corner of pond. The Ash Pond area is grown over with heavy brush
and vegetation with the exception of the ponding area.
H&H Evaluation Criteria
North Carolina's Department of Environmental Quality (NCDEQ) Dam Safety has adopted the
Federal CCR Rule and per the dam safety High Hazard Classification, each ash basin is now
required to pass a full Probable Maximum Precipitation (PMP). Each basin is classified as high
hazard by NCDEQ due to the potential for environmental impacts greater than $200,000, if the
basin failed.
The computer program HydroCAD Version 10.0 was initially used to perform the H&H
calculations to determine if the current conditions could safely store the revised design storm
(full PMP storm event) without an uncontrolled discharge. Previously, the design storm was
listed as the'/2 PMP storm event. NCDEQ has requested that the supporting modeling
information be provided in either HEC-RAS or HEC-HMS format. In accordance with the new
guidelines, the Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS, version
4.3) computer program was used to perform the hydrologic & hydraulic (H&H) calculations.
The existing conditions for the Ash Pond was obtained from best available reports and
topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation Cape Fear Ash
Ponds, McKim and Creed Topographic Survey (2014), and LiDAR Topographic Survey by WSP
(2015).

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1978 Ash Pond H&H Update
Page 3 Wood E&IS Project No. 7812-19-0142
The Cape Fear Ash Ponds are classified as high hazard, with the revised regulatory design storm
for the ponds of the full PMP storm event. Based on the Hydrometeorological Report No. 51,
Probable Maximum Precipitation Estimates, United States East of the 105th Meridian, from the
National Oceanic and Atmospheric Administration (Figure 18: All -Season PMP (in.) for 6 hr 10
mil) the PMP for the Cape Fear site is as follows:
• PMP = 29.50 inches of rainfall for 6 hours
Since there is no outlet structure for the basin, the basin is required to store 2x the full PMP storm
event. Based on field observations and aerial imagery, the basin was assigned appropriate curve
numbers (CN) for the general condition of land covers with an appropriate time of concentration
calculated for each area by using TR-55 recommendations.
The storage for the basin was developed from the assumed initial water elevation to the top of
dam. The storage for the basin was estimated using the prismatic volume calculation method
with the elevation -surface area input data. Storage volumes were determined from contours
derived from the existing conditions. The 1978 Ash Pond has an active pumping (with treatment)
system, that generally keeps the pond pumped down to the minimum permissible depth
(approximately 3 feet in the deepest area of the basin). Additional ponding area details can be
found in the modeling results.
The H&H Analysis was conducted for the stage -storage conditions, with no outlet structure in
operation. The basin is filled with ash, and stormwater would likely infiltrate into the underlying
ash material during a storm event. However, for the purpose of this analysis, it is assumed that
no infiltration occurs. A minimum time of concentration (Tc) was calculated for the pond consistent
with T-55 methods in HydroCAD. The length of the flow paths of sheet flow, shallow concentrated
flow, and channel flow as well as slope and channel characteristics were determined based on
the topography, which is consistent with TR-55 recommendations. Additional details on time of
concentration for each pond can be found in the modeling HydroCAD results. The storage for the
basin was estimated using the prismatic volume calculation method with the elevation -surface
area input data. Storage volumes for the 1978 Ash Pond were determined from contours derived
from the McKim and Creed Topographic Survey (2014), and LiDAR Topographic Survey by WSP
(2015). Additional ponding area details can be found in the modeling results. Wood E&IS
assumed a Type II storm distribution for the 6-hr peak hydrograph.
In order to support the request by NCDEQ to model the basin in HEC-HMS format, the existing
hydraulic models created in HydroCAD were re-created using HEC-HMS version 4.3. The HEC-
HMS models were developed using inputs from the existing HydroCAD models to the greatest
extent possible. At a minimum, the following inputs required for the development of the HEC-
HMS model were utilized:
• Rainfall data, curve numbers, time of concentration for hydrologic computations
• Stage -Storage rating curves for the ash ponds
• Outlet rating curves
H&H Summary
Using the information above and the design storm hydrograph, Wood E&IS completed the H&H
Analyses using HEC-HMS version 4.3 and ran the models for 360 hours (15 days) to allow

Duke Energy Cape Fear Plant
March 28, 2019 Cape Fear 1978 Ash Pond H&H Update
Page 4 Wood E&IS Project No. 7812-19-0142
sufficient time for 80% drawdown. The results of the analyses are shown below in Table 1. The
current conditions allow for the storage of back-to-back design storms (PMP storm event) within
the basin. The subsequent release of the stormwater requires implementation of the Pumping
Plan.
Table 1. Modeling Results
Updated Results
1978 Ash Pond
Full PMP Storm Event
1978 Ash Pond
2x Full PMP Storm
Event3P)
Peak Stage during OF (ft)
190.1
193.8
Minimum Dike Elevation (ft)
194.0
194.0
Pond Freeboard (ft)
3.9
0.2
100% Inflow Volume (acre-ft)
88.7
177.1
80% Inflow Volume (acre-ft)
71.0
141.7
80% Discharge Time (hr)
N/A -Pumping
N/A -Pumping
According to Dam Safety 15A NCAC 2K.0205, the spillway system shall be capable of removing
at least 80 percent of the water temporarily detained above the elevation of the primary spillway
within 15 days following passage of the design storm peak. There is no spillway associated with
the 1978 Ash Basin. The release of all stormwater is accomplished via pumping to the on -site
treatment system which is discharged to the Cape Fear River. Thus, the ash basin is compliant
with 15A NCAC 2K.0205. The results for the calculations are attached.
Conclusion
Based on the results of this study and considering the conservative assumption made (no
infiltration) Wood E&IS concludes the existing conditions will safely store the design storm event
(2x full PMP) without an uncontrolled discharge. Drawdown requirements per 15A NCAC 2K
0.0205 are met through the Pumping Plan.
Closing
Wood E&IS appreciates the opportunity to offer our services on this project. If you have
any questions concerning this response, please contact us.

Duke Energy
March 28, 2019
Page 5
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
bl�41140
William A. Williams, PE, PG
Senior Engineer
HEC-HMS model files provided separately
Cape Fear Plant
Cape Fear 1978 Ash Pond H&H Update
Wood E&IS Project No. 7812-19-0142
%40aE@43F Cry d li 17 P fP' /fPPP
10
n
Jeffery Mann, PE
Chief Engineer

wood.
April 30, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Cape Fear 1985 Ash Pond H&H Update
Summary of Supporting H&H Analyses
Duke Energy — Cape Fear Steam Station
Chatham County, North Carolina
Wood E&IS Project No. 7812-19-0142
Dear Mr. Smith,
As authorized by Duke Energy Carolinas, LLC (Duke Energy), Wood Environment & Infrastructure
Solutions, Inc. (Wood E&IS) has revised the Hydraulic and Hydrologic analysis (H&H) based upon
a full Probable Maximum Precipitation (PMP) rainfall event to determine if the ash basins located
at the Cape Fear Steam Station have sufficient capacity for the design storm with the current
outlet conditions.
Background Information
The Cape Fear Plant is located at 500 CP&L Road near Moncure, North Carolina, and is
reported to have begun commercial operation in 1923. Two of the original coal-fired generating
units were retired in 1977 and two additional units were retired in 2011. The remaining two
units, along with one of four oil -fired combustion turbine units on site, were retired in October
2012. There are five Ash Pond Areas located at the Cape Fear Plant. Ash material or coal
combustion residuals (CCR) has historically been deposited within the Ash Ponds located on
site by hydraulic sluicing operations for both fly ash and bottom ash material. There are no
longer any ash disposal operations with the Ash Pond areas with the permanent retirement of
the fossil generating units.
The 1985 Ash Pond area is located on the southeast corner of the plant, east of the 1978 Ash
Pond area, and adjacent to the Cape Fear Plant discharge canal.
Correspondence:
Wood Environment &Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
•
Licensure NC Engineering F-1253 NC Geology C-247

Duke Energy
April 30, 2019
Page 2
Cape Fear Plant
Cape Fear 1985 Ash Pond H&H Update
Wood E&IS Project No. 7812-19-0142
The 1985 Ash Pond operates under a National Pollutant Discharge Elimination System
(NPDES) permit number NC0003433 issued by the North Carolina Department of Environment
and Natural Resources (NCDENR) Division of Water Quality as a water treatment unit. The
basin exterior embankment is regulated by NCDENR Division of Energy, Mineral and Land
Resources, Land Quality Section, Dam Safety Program as an Intermediate Hazard Dam, and is
identified in the regulatory program as "Cape Fear 1985 Ash Pond Dam" (State I.D. No.
CHATH-079).
From review of available descriptive information, the 1985 Ash Pond has a surface area of
about 60 acres, maximum dike height of about 28 feet, crest width of 15 feet, crest level at
Elevation 194 feet, and dike length of approximately 7,400 feet. The upstream (interior) slope is
reported to be 2:1, and the downstream (exterior) slope is reported to be in the range of 2:1 to
4:1.
The original design was reported to have been provided by CP&L with technical support from
William L. Wells. Records for design are available for review including geotechnical
investigation documentation. There are no provisions for seepage control (internal drain or
blanket) provided for the dike based on review of available design information.
The Ash Pond area was constructed between 1984 and 1985. The original design was
developed by CP&L, and construction was performed by W.D. Flower, Inc. under the
supervision of CP&L. Based upon review of available design information there are no
provisions for seepage control within the ash pond area. In the 2006 to 2007 timeframe, and
interior ash storage area was constructed within the Ash Pond area. The interior ash storage
area has a discharge outlet structure that discharges within the 1985 Ash Pond. In 2010, AMEC
(Wood E&IS) provided a plan for ash restacking within the interior ash storage area.
The 1985 Ash Pond outlet structure is located at the southwest corner of the pond. Discharge
from this outlet structure flows in a concrete lined channel and is discharged into the Cape Fear
plant discharge canal. A closed, locked gate valve was installed on the downstream discharge
piping in 2015. The majority of the 1985 Ash Pond area is filled with sedimented ash and
receives inflow only from rainfall over the pond area. Rainfall on the pond collects in the
southwest corner of the 1985 Ash Pond.
H&H Evaluation Criteria
North Carolina's Department of Environmental Quality (NCDEQ) Dam Safety has adopted the
Federal CCR Rule and per the dam safety High Hazard Classification, each ash basin is now
required to pass a full Probable Maximum Precipitation (PMP). Each basin is classified as high
hazard by NCDEQ due to the potential for environmental impacts greater than $200,000, if the
basin failed.
The computer program HydroCAD Version 10.0 was initially used to perform the H&H calculations
to determine if the current conditions (revised per updated survey information) could safely store
the revised design storm (full PMP storm event) without an uncontrolled discharge. Previously,
the design storm was listed as the '/2 PMP storm event. NCDEQ has requested that the
supporting modeling information be provided in either HEC-RAS or HEC-HMS format. In
accordance with the new guidelines, the Hydrologic Engineering Center Hydrologic Modeling

Duke Energy Cape Fear Plant
April 30, 2019 Cape Fear 1985 Ash Pond H&H Update
Page 3 Wood E&IS Project No. 7812-19-0142
System (HEC-HMS, version 4.3) computer program was used to perform the hydrologic &
hydraulic (H&H) calculations.
The existing conditions for the Ash Ponds were obtained from best available reports and
topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation Cape Fear Ash
Ponds, McKim and Creed Topographic Survey (2014), and LiDAR Topographic Survey by WSP
(2015).
The Cape Fear Ash Ponds are classified as high hazard, with the revised regulatory design storm
for the ponds of the full PMP storm event. Based on the Hydrometeorological Report No. 51,
Probable Maximum Precipitation Estimates, United States East of the 105th Meridian, from the
National Oceanic and Atmospheric Administration (Figure 18: All -Season PMP (in.) for 6 hr 10
miz) the PMP for the Cape Fear site is as follows:
• PMP = 29.50 inches of rainfall for 6 hours
Since the gate valve on the discharge culvert remains locked in the closed position, the basin is
required to store back-to-back PMP storm events.
Based on field observations and aerial imagery, each of the sub basins were assigned appropriate
curve numbers (CN) for the general condition of land covers with an appropriate time of
concentration calculated for each area by using TR-55 recommendations.
The storage for each basin was developed from the assumed initial water elevation (162.5') to
the top of dam. The storage for the basin was estimated using the prismatic volume calculation
method with the elevation -surface area input data. Storage volumes were determined from
contours derived from the existing conditions. The 1985 Ash Pond has an active pumping (with
treatment) system, that generally keep the pond pumped down to the minimum permissible depth
(approximately 3 feet in the deepest area of the basin, correlating to an elevation of 162.5').
Additional ponding area details can be found in the modeling results.
The H&H Analysis was conducted for the proposed stage -storage conditions and Table 1 provides
information on the current outlet structure. The 1985 Ash Pond has a gate -valve installed on the
downstream outlet pipe, which remains in the closed (locked) condition. The H&H Analysis was
conducted for the stage -storage conditions, with the outlet structure both in and not in operation.
The 1985 Ash Pond has an active pumping (with treatment) system, that generally keeps the
pond pumped down to the minimum permissible depth (approximately 3 feet in the deepest area
of the basin).
Table 1. 1985 Ash Pond Outlet Existing Conditions
1985 Ash Pond
Characteristic
Existing
Dike Crest Elevation (ft)
192.0
Culvert Diameter (in)
48
Culvert Elevation (ft)
188.10
Culvert Material
RCP

Duke Energy Cape Fear Plant
April 30, 2019 Cape Fear 1985 Ash Pond H&H Update
Page 4 Wood E&IS Project No. 7812-19-0142
The basins are generally filled with ash, and stormwater would likely infiltrate into the underlying
ash material during a storm event. However, for the purpose of this analysis, it is assumed that
no infiltration occurs. A water ponding area is located in the southeast corner of the 1985 Ash
Pond. A minimum time of concentration (Tc) was calculated for the pond consistent with T-55
methods in HydroCAD. The length of the flow paths of sheet flow, shallow concentrated flow, and
channel flow as well as slope and channel characteristics were determined based on the
topography, which is consistent with TR-55 recommendations. Additional details on time of
concentration for each pond can be found in the modeling HydroCAD results. The storage for
each basin was estimated using the prismatic volume calculation method with the elevation -
surface area input data. Storage volumes for the 1985 Ash Pond were determined from contours
derived from the McKim and Creed Topographic Survey (2014), and LiDAR Topographic Survey
by WSP (2015). Additional ponding area details can be found in the modeling results. Wood E&IS
assumed a Type II storm distribution for the 6-hr peak hydrograph.
In order to support the request by NCDEQ to model the basin in HEC-HMS format, the existing
hydraulic models created in HydroCAD were re-created using HEC-HMS version 4.3. The HEC-
HMS models were developed using inputs from the existing HydroCAD models to the greatest
extent possible. At a minimum, the following inputs required for the development of the HEC-
HMS model were utilized:
• Rainfall data, curve numbers, time of concentration for hydrologic computations
• Stage -Storage rating curves for the ash ponds
• Outlet rating curves
H&H Summary
Using the information above and the design storm hydrograph, Wood E&IS completed the H&H
Analysis using HEC-HMS version 4.3. Results of the analyses are shown below in Table 2. The
current conditions allow for the capture of both the initial PMP storm event and the second PMP
storm event within the basin. The subsequent release of the stormwater requires implementation
of the Pumping Plan.
Table 2. Modeling Results
Updated Results
1985 Ash Pond
Full PMP Storm Event
1985 Ash Pond
2x Full PMP Storm Event
Peak Stage during IDF (ft)
179.9
190.7
Minimum Dike Elevation (ft)
192.95
192.95
Pond Freeboard (ft)
13.05
2.25
100% Inflow Volume (acre-ft)
142.5
289.3
80% Inflow Volume (acre-ft)
114.0
231.4
80% Discharge Time (hr)
N/A
N/A

Duke Energy Cape Fear Plant
April 30, 2019 Cape Fear 1985 Ash Pond H&H Update
Page 5 Wood E&IS Project No. 7812-19-0142
According to Dam Safety 15A NCAC 2K.0205, the spillway system shall be capable of removing
at least 80 percent of the water temporarily detained above the elevation of the primary spillway
within 15 days following passage of the design storm peak. The gate valve on the discharge
culvert is locked in the closed position. The 1985 Ash Basin safely stores the back-to-back PMP
design storm events. Thus, the current structure is compliant with 15A NCAC 2K.0205.
Implementation of the pumping plan for the basin is required for removal of the stormwater. The
results for the calculations are attached.
Conclusion
Based on the results of this study and considering the conservative assumption made (no
infiltration) Wood E&IS concludes the existing conditions will safely contain back-to-back design
storm events (full PMP) without an uncontrolled discharge. Drawdown requirements per 15A
NCAC 2K 0.0205 are met through the Pumping Plan.
Closing
Wood EMS appreciates the opportunity to offer our services on this project. If you have
any questions concerning this response, please contact us.
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
William A. Williams, PE, PG
Senior Engineer
HEC-HMS model files provided separately
J effei
Chief Engineer

wood.
October 11, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Hydrology and Hydraulics Analysis Summary Report
1956 Ash Basin Decommissioning (CHATH-075)
Duke Energy — Cape Fear Steam Station
Moncure County, North Carolina
Wood Project No. 7812180071
Dear Mr. Smith,
As part of the decommissioning plan for the Cape Fear 1956 Ash Basin (CHATH-075), Wood
Environment & Infrastructure Solutions, Inc. (Wood) has prepared this Hydraulic and Hydrologic
analysis (H&H) summary report. This H&H summary represents the 1956 Ash Basin in the
proposed decommissioned condition.
Background Information
The Cape Fear Plant began power operations in 1923. Additional power generating units were
added from 1924 to 1969. In the most recent operating configuration, the Plant employed two
coal-fired units along with four oil -fueled combustion turbine units. Ash material generated from
coal combustion was transported by sluicing to and stored in five on -site ash basins. Power
generating operations were terminated at the Plant in October 2012 and demolition was
completed in 2017.
There are no longer any ash disposal operations within the ash basin areas with the permanent
retirement of the coal-fired units. The ash basins at the Cape Fear Plant are surrounded by
perimeter dikes such that no stormwater flows into the basins.
The 1956 Ash Basin area is located at the northwest corner of the Plant adjacent to the Haw
River and near the confluence with the Deep River that then forms the Cape Fear River. From
review of available descriptive information, this basin has a surface area of about 12 acres,
maximum dike height of about 20 feet, crest width in the range of 7-10 feet, crest level in the
range of Elevation 182-190 feet, and dike length of approximately 3,200 feet. The upstream
(interior) slope is reported to be about 2(horizontal): 1 (vertical), and the downstream (exterior)
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodplc.com
Licensure: NC Engineering F-1253 NC Geology C-247
0

Duke Energy
October 11, 2019
Page 2
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
slope is reported to be in the range of 1:1 to 1.5:1. The dike along the southeast side of the Ash
Pond was formed by the plant flood protection levee. There are no records available for design
and construction of the 1956 Ash Pond.
H&H Evaluation Criteria
The computer program HEC-HMS was used to perform the H&H calculations to route the
design storm through the ash basin, to identify the hydraulic conditions within the basin for the
proposed decommissioned condition. The 1956 Ash Basin, in the decommissioned conditions,
will consist of the basin dikes with an opening (breach) in the northwestern dike section. The
dike opening is designed to be approximately 35 feet wide, cut to an elevation of 168.0 feet.
The 1956 Ash Basin design storm for the decommissioned condition is the 100-year storm
event, which equates to 7.74 inches of rainfall for a 24-hour period.
H&H Summary
Using the information above and the design storm hydrograph, the design storm safely passes
the decommissioned condition for the basin. A summary of the H&H modeling is provided in
Table 1.
Table 1 - H&H Results
Results for Decommissioned
Condition
Weatherspoon
Ash Basin
Peak Water Elevation (ft)
169.2
Weir (Opening) Elevation (ft)
168.0
Dike Crest Elevation (ft)
182-190
Pond Freeboard (ft)
12.8-20.8
Peak Discharge Rate (ft3/s)
143.9
Peak Velocity (ft/s)
3.43
Conclusion
Based on the results of this H&H analysis, Wood concludes that the decommissioned ash basin
with safely pass the design storm event without overtopping the remaining dike remnants.
Furthermore, the discharge velocity through the dike opening should not cause erosive
conditions across the weir section or adjacent dike slopes.

Duke Energy
October 11, 2019
Page 3
Closing
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
Wood appreciates the opportunity to offer our services on this project. If you have any
questions concerning this response, please contact us.
Sincerely, , %A CAR �
Wood Environment & Infrastructure Solutions, Inc. ���`_0 ...••..,�Z. ;Skk
9
Rahish Khatri, PE
Project Engineer
Jeffery
Projec)
Attachments H&H Calculation — Decommissioned Conditions
11

Reservoir "1956 Ash Pond'' Results for Run''100 year"
.05
F
h
oy
168
.04
168
a
03
02
t
f•
168
168
01
.00
_ _ _ _ _
_..................
_ _ _ _
....................
_ — — —
...... _..........
!.
_.�
..- ..
.._._
.......
_ ......................
......................
_ _ _
.....................
_ _-_ — —
....................
168
��
140
120
100
80
60
40
20
0
llll'u, ul.uu tm'tlll
Legend[Co ET-2]S,2019, 13:09:59)
------ Run.108 year Element:195fi Ash Pond Result5[orage
--- Run.108 year Element:1955 Ash Pond Result. Combined Inflow
VQIE ]5301', Began computing simulation run'100 year'attime 2]SepLl19�13',�9:59,
lJsl'lJll lL'lJll 'I J'lJll lif'W Ll'llll lHl'll ll
01Jan2000
Run:100 year Element:1956 Ash Pond Result:Pool Elevation Run.l80year Element:l956Ash Pond Result Outflow
20
97
73
r
50
27
03
0 Summary ResuIts far Reser,rair "195GAsh Pand" F El F"
Project: 56 Pond Simulation Run: 100 year
Reservoir: 1956 Ash Pond
Start of Run; O1Jan2000r 00:00 Basin Model: 56 Pond
End of Run: 02Jan2000r 00:00 Meteorologic Model: 100 year
Compute Time:27Sep2019r 13:09: 59 Control Specifications:24 hour
Volume Units: 0 AC -FT
Computed Results
Peak Inflo-1 143.0 (CFS) Date f rme of Peak Inflow: 013an2000r 11:53
Peak Discharge: 143.9 (CFS) Date f rme of Peak Discharge: 01Jan2000r 11:54
Inflow Volume: 7.74 (IN) Peak Storage: 0.1 (ACC
Discharge Volume:7.74 (IN) Peak Elevation: 169.2 (M
ar HMS Results at Ash Pond 1956

wood.
October 11, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Hydrology and Hydraulics Analysis Summary Report
1963/70 Ash Basin Decommissioning (CHATH-076/77)
Duke Energy — Cape Fear Steam Station
Moncure County, North Carolina
Wood Project No. 7812180071
Dear Mr. Smith,
As part of the decommissioning plan for the Cape Fear 1963/70 Ash Basin (CHATH-076/77),
Wood Environment & Infrastructure Solutions, Inc. (Wood) has prepared this Hydraulic and
Hydrologic analysis (H&H) summary report. This H&H summary represents the 1963/70 Ash
Basin in the proposed decommissioned condition.
Background Information
The Cape Fear Plant began power operations in 1923. Additional power generating units were
added from 1924 to 1969. In the most recent operating configuration, the Plant employed two
coal-fired units along with four oil -fueled combustion turbine units. Ash material generated from
coal combustion was transported by sluicing to and stored in five on -site ash basins. Power
generating operations were terminated at the Plant in October 2012 and demolition was
completed in 2017.
There are no longer any ash disposal operations within the ash basin areas with the permanent
retirement of the coal-fired units. The ash basins at the Cape Fear Plant are surrounded by
perimeter dikes such that no stormwater flows into the basins.
The combined 1963 and 1970 Ash Basin area is located on the southwest corner of the site
adjacent to the east bank of the Cape Fear River.
From review of available descriptive information, the 1963 Ash Basin has a surface area of
about 21 acres, maximum dike height of about 22 feet, crest width in the range of 12-14 feet,
crest level at Elevation 197 feet, and dike length of approximately 4,000 feet. The upstream
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodplc.com
Licensure: NC Engineering F-1253 NC Geology C-247

Duke Energy Cape Fear Station
October 11, 2019 Hydrology and Hydraulics Analysis Summary Report
Page 2 Wood Project No. 7812180071
(interior) slope is reported to be in the range of 1.5:1 to 2:1, and the downstream (exterior) slope
is reported to be 1.5:1.
From review of available descriptive information, the 1970 Ash Basin has a surface area of
about 30 acres, maximum dike height of about 27 feet, crest width in the range of 12-14 feet,
crest level at Elevation 197 feet, and dike length of approximately 4,600 feet. The upstream
(interior) slope is reported to be about 2:1, and the downstream (exterior) slope is reported to be
2:1.
The original 1963 Ash Basin area was constructed with a crest level at Elevation 188 feet. The
perimeter enclosure dikes for the 1963 Ash Basin were extended and incorporated into the 1970
Ash Basin to form the current combined area. The crest level for the combined 1963/1970 Ash
Basin area is at Elevation 197 feet. The crest level for the 1963 Ash Basin area was raised from
Elevation 188 feet to Elevation 197 feet when the two Ash Basin areas were combined. The
common separating dike originating from the 1963 Ash Basin area was removed to the allow
flow to pass into the 1970 Ash Basin area. Remnants of the original separating dike have been
observed from field inspections. There are limited records available for design of the 1963 and
1970 Ash Basins.
The original discharge outlet structure for the 1963 Ash Basin consisted of an 18-inch diameter
reinforced concrete riser and discharge pipe, located on the separation dike between the 1963
Ash Basin and 1970 Ash Basin areas. The original discharge outlet structure for the 1963 Ash
Basin area was abandoned after combining the two ash basin areas; however, there are no
records available to document the abandonment procedure for the original discharge outlet
structure. The 1970 Ash Basin area has a discharge outlet structure at the southwest corner of
the 1970 Ash Basin which originally consisted of an 18-inch diameter reinforced concrete riser
and discharge pipe. In 1983, a new discharge pipe and outlet structure were designed for the
1970 Ash Basin, which included a concrete 3.5 ft x 3.5 ft (nominal) riser box and a 20-inch
diameter fiberglass reinforced plastic (FRP) discharge pipe. Flow from the discharge outlet
structure was released to the Cape Fear River. In October 2015, 20-inch FRP pipe was
replaced with a 32-inch High Density Polyethylene (HDPE) pipe.
H&H Evaluation Criteria
The computer program HEC-HMS was used to perform the H&H calculations to route the
design storm through the ash basin, to identify the hydraulic conditions within the basin for the
proposed decommissioned condition. The 1963/70 Ash Basin, in the decommissioned
conditions, will consist of the basin dikes with an opening (breach) in the western dike section.
The dike opening is designed to be approximately 125 feet wide, cut to an elevation of 161.0
feet.
The 1963/78 Ash Basin design storm for the decommissioned condition is the 100-year storm
event, which equates to 7.74 inches of rainfall for a 24-hour period.

Duke Energy
October 11, 2019
Page 3
H&H Summary
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
Using the information above and the design storm hydrograph, the design storm safely passes
the decommissioned condition for the basin. A summary of the H&H modeling is provided in
Table 1.
Table 1 - H&H Results
Results for Decommissioned
Condition
Weatherspoon
Ash Basin
Peak Water Elevation (ft)
161.3
Weir (Opening) Elevation (ft)
161.0
Dike Crest Elevation (ft)
188-197
Pond Freeboard (ft)
26.7-35.7
Peak Discharge Rate (ft3/s)
62.4
Peak Velocity (ft/s)
1.67
Conclusion
Based on the results of this H&H analysis, Wood concludes that the decommissioned ash basin
with safely pass the design storm event without overtopping the remaining dike remnants.
Furthermore, the discharge velocity through the dike opening should not cause erosive
conditions across the weir section or adjacent dike slopes.
Closing
Wood appreciates the opportunity to offer our services on this project. If you have any
questions concerning this response, please contact us.
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
Rahish Khatri, PE
Project Engineer
Proj
Attachments H&H Calculation — Decommissioned Conditions
EALY41-
934
YA,N�

LLEtwi '
Reservoir " 1 P' Results for Run "100 year"
0.18
161.300
014
161222
0.12
Q
I%
161.183
a10
m
I
1
161144
'L
0.08
161.106
...........
-
0.04.
•..
161.028
002
160 989
......................................
60
50
40
g 30
20
10
0
00:00 03:00 06:00 09:00 12.00 1500 18.00 21:00 0000
01J-2000
Legend (Compute Tme, =,PMA, 13:94:11)
------ Run.100 year ElemertlP ResultStorage Run.100 year Element lP Result: Pool Elevation — Run100year ElementlP Re,uItOutfl— --- Run:100 year ElementlP ResultC—b—d Inflow
0 Summary Results far Reservoir "1 P" p
Project: Basin63_70 Simulation Run: 100 year
Reservoir: 1P
Start of Run: 01Jan2000r 00:00 Basin Model: Basin1963_70
End of Run: 02Jan2000r 00:00 Meteorologic Model: 100 year
Compute Tiime:27Sep2019, 13:44:11 Control Spedfications:PMPControl
Volume Units: • AC -FT
Computed Results
Peak Inflow; 62.4 (CFS) Date f rme of Peak Inflow: 013an2000r 13:40
Peak Discharge: 62.4 (CFS) Date[Time rme of Peak Discharge: 01Jan2000 f 13:4.3
Inflow Volume: 4.49 (IN) Peak Storage: 0.2 {ACC
Discharge Volume:4,48 ON) Peak Elevation: 161.3 (M
100 vear HMS Results at Ash Pond 1963-70

wood.
October 11, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Hydrology and Hydraulics Analysis Summary Report
1978 Ash Basin Decommissioning (CHATH-078)
Duke Energy — Cape Fear Steam Station
Moncure County, North Carolina
Wood Project No. 7812180071
Dear Mr. Smith,
As part of the decommissioning plan for the Cape Fear 1978 Ash Basin (CHATH-078), Wood
Environment & Infrastructure Solutions, Inc. (Wood) has prepared this Hydraulic and Hydrologic
analysis (H&H) summary report. This H&H summary represents the 1978 Ash Basin in the
proposed decommissioned condition.
Background Information
The Cape Fear Plant began power operations in 1923. Additional power generating units were
added from 1924 to 1969. In the most recent operating configuration, the Plant employed two
coal-fired units along with four oil -fueled combustion turbine units. Ash material generated from
coal combustion was transported by sluicing to and stored in five on -site ash basins. Power
generating operations were terminated at the Plant in October 2012 and demolition was
completed in 2017.
There are no longer any ash disposal operations within the ash basin areas with the permanent
retirement of the coal-fired units. The ash basins at the Cape Fear Plant are surrounded by
perimeter dikes such that no stormwater flows into the basins.
The 1978 Ash Basin area is located south of the Plant facility, on the east side of the 1963/1970
Ash Basin area, and adjacent to the discharge canal.
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodplc.com
Licensure: NC Engineering F-1253 NC Geology C-247
0

Duke Energy
October 11, 2019
Page 2
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
From review of available descriptive information, this 1978 Ash Basin has a surface area of
about 35 acres, maximum dike height of about 27 feet, crest width of 15 feet, crest level at
Elevation 197 feet, and dike length of approximately 5,600 feet. The upstream (interior) slope is
reported to be 2:1, and the downstream (exterior) slope is reported to be 2:1.
The 1978 Ash Basin was formed by incorporating a portion of the 1963/1973 Ash Basin dike on
the west side, and constructing new dikes on the north, south and east sides. Design was
reported to have been provided by CP&L with technical support from William L. Wells. Limited
records for design and construction are available for review. There are no provisions for
seepage control (internal drain or blanket) provided for the dike based on review of available
design information.
H&H Evaluation Criteria
The computer program HEC-HMS was used to perform the H&H calculations to route the
design storm through the ash basin, to identify the hydraulic conditions within the basin for the
proposed decommissioned condition. The 1978 Ash Basin, in the decommissioned conditions,
will consist of the basin dikes with an opening (breach) in the southern dike section. The dike
opening is designed to be approximately 90 feet wide, cut to an elevation of 170.0 feet.
The 1978 Ash Basin design storm for the decommissioned condition is the 100-year storm
event, which equates to 7.74 inches of rainfall for a 24-hour period.
H&H Summary
Using the information above and the design storm hydrograph, the design storm safely passes
the decommissioned condition for the basin. A summary of the H&H modeling is provided in
Table 1.
Table 1 - H&H Results
Results for Decommissioned
Condition
Weatherspoon
Ash Basin
Peak Water Elevation (ft)
170.7
Weir (Opening) Elevation (ft)
170.0
Dike Crest Elevation (ft)
791.0
Pond Freeboard (ft)
26.3
Peak Discharge Rate (ft3/s)
156.1
Peak Velocity (ft/s)
2.48

Duke Energy
October 11, 2019
Page 3
Conclusion
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
Based on the results of this H&H analysis, Wood concludes that the decommissioned ash basin
with safely pass the design storm event without overtopping the remaining dike remnants.
Furthermore, the discharge velocity through the dike opening should not cause erosive
conditions across the weir section or adjacent dike slopes.
Closing
Wood appreciates the opportunity to offer our services on this project. If you have any
questions concerning this response, please contact us.
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
All-�
Rahish Khatri, PE
Project Engineer
"dPdfll3ifa''�'�
Attachments H&H Calculation — Decommissioned Conditions

LM G,aphf, Resery '1978&s Pond" C"
Re rvoh "1978 Ash Pond" Results (or Run "100 year"
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01Jan255
Legend (Compute Tme', 2]Sep2019 13',33',30J
...... Run_100 yeas Element1978 Ash Pand Result_Sto..p --- Run_105 year Element_1978 Ash Pand Result Pool Elevation — Run_100 yea, Element1978 Ash Pand R—It_0,,0-
--- Run_180 yea, Element1978 Ash Pand Result_Comhined I,n-
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0 Summary ResuIts for Reservoir "1978Ash Pond°
Project: 78_Pond Simulation Run: 100 year
Reservoir: 1978 Ash Pond
Start of Run; 01Jan2000, 00:00 Basin Model: 78 Pond
End of Run: 023an2000, 00:00 Meteorologic Model: 100 year
Compute Time:27Sep2019, 1133:30 Control Spedfications:PMP Events
Volume Units: • .N. 0 AC -FT
Computed Results
Peak Inflow: 190.2 (CFS) Date/Time of Peak Inflow: 01Jan2000, 12-:02
Peak Discharge: 156.1 (CFS) Date f rme of Peak Discharge: 01Jan2000, 12-:17
Inflow Volume: 7.71 (IN) Peak Storage: 19 {AC+—o
Discharge Volume:7.61 4IN) Peak Elevation: 1.70.7 AFT)
100 year HMS Results at Ash Pond 1978

wood.
October 11, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: Hydrology and Hydraulics Analysis Summary Report
1985 Ash Basin Decommissioning (CHATH-079)
Duke Energy — Cape Fear Steam Station
Moncure County, North Carolina
Wood Project No. 7812180071
Dear Mr. Smith,
As part of the decommissioning plan for the Cape Fear 1985 Ash Basin (CHATH-079), Wood
Environment & Infrastructure Solutions, Inc. (Wood) has prepared this Hydraulic and Hydrologic
analysis (H&H) summary report. This H&H summary represents the 1985 Ash Basin in the
proposed decommissioned condition.
Background Information
The Cape Fear Plant began power operations in 1923. Additional power generating units were
added from 1924 to 1969. In the most recent operating configuration, the Plant employed two
coal-fired units along with four oil -fueled combustion turbine units. Ash material generated from
coal combustion was transported by sluicing to and stored in five on -site ash basins. Power
generating operations were terminated at the Plant in October 2012 and demolition was
completed in 2017.
There are no longer any ash disposal operations within the ash basin areas with the permanent
retirement of the coal-fired units. The ash basins at the Cape Fear Plant are surrounded by
perimeter dikes such that no stormwater flows into the basins.
The 1985 Ash Basin area is located on the southeast corner of the Plant, east of the 1978 Ash
Basin area, and adjacent to Corinth Road.
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodplc.com
Licensure: NC Engineering F-1253 NC Geology C-247
0

Duke Energy
October 11, 2019
Page 2
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
From review of available descriptive information, this 1985 Ash Basin has a surface area of
about 60 acres, maximum dike height of about 28 feet, crest width of 15 feet, crest level at
Elevation 194 feet, and dike length of approximately 7,400 feet. The upstream (interior) slope is
reported to be 2:1, and the downstream (exterior) slope is reported to be in the range of 2:1 to
4:1.
The original design was reported to have been provided by CP&L with technical support from
William L. Wells. Records for design are available for review including geotechnical investigation
documentation. There are no provisions for seepage control (internal drain or blanket) provided
for the dike based on review of available design information.
The discharge outlet structure consists of a 48-inch diameter reinforced concrete drop inlet riser
with a 30-inch diameter reinforced concrete outlet pipe. Flow from the outlet structure is
discharged to the plant discharge canal. Standing water is present at the southwest end of the
Ash Basin area near the discharge outlet structure. A gate valve was installed on the discharge
pipe to ensure that no unauthorized release of water from the basin will occur. This valve
remains in the closed position and is locked.
H&H Evaluation Criteria
The computer program HEC-HMS was used to perform the H&H calculations to route the
design storm through the ash basin, to identify the hydraulic conditions within the basin for the
proposed decommissioned condition. The 1985 Ash Basin, in the decommissioned conditions,
will consist of the basin dikes with an opening (breach) in the southern dike section. The dike
opening is designed to be approximately 150 feet wide, cut to an elevation of 169.0 feet.
The 1985 Ash Basin design storm for the decommissioned condition is the 100-year storm
event, which equates to 7.74 inches of rainfall for a 24-hour period.
H&H Summary
Using the information above and the design storm hydrograph, the design storm safely passes
the decommissioned condition for the basin. A summary of the H&H modeling is provided in
Table 1.

Duke Energy
October 11, 2019
Page 3
Conclusion
Cape Fear Station
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180071
Table 1 - H&H Results
Results for Decommissioned
Condition
Weatherspoon
Ash Basin
Peak Water Elevation (ft)
169.6
Weir (Opening) Elevation (ft)
169.0
Dike Crest Elevation (ft)
194.0
Pond Freeboard (ft)
24.4
Peak Discharge Rate (ft3/s)
213.2
Peak Velocity (ft/s)
2.37
Based on the results of this H&H analysis, Wood concludes that the decommissioned ash basin
with safely pass the design storm event without overtopping the remaining dike remnants.
Furthermore, the discharge velocity through the dike opening should not cause erosive
conditions across the weir section or adjacent dike slopes.
Closing
Wood appreciates the opportunity to offer our services on this project. If you have any
questions concerning this response, please contact us.
i,,,��lllllll//►/��
Sincerely,
Wood Environment & Infrastructure Solutions, Inc.
$ ro
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Sq e
Rahish Khatri, PE Jeffew�°�'�II�It�
Project Engineer Proj c a
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Attachments H&H Calculation — Decommissioned Conditions

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— Rut 100 year ElementAsh Pond 1P ResultO,tl—
71 Summary ResuIts for ReservoR "Ash Pond 1P"F= p
Project; Basin 1985 Simulation Run; 100 rear
Reservoir: Ash Pond 1P
Start of Run; 011an2050r 00;00 Basin Model; Basin 1985
End of Run; 02Jan2050, 00:00 Meteorologic Model; 100 year
Compute Time; 27Sep2019r I156:38 Control Spedfications;Control
Volume Units; # AC -FT
Computed Results
Peak Inflow: 267.8 (CFS) Date/Time of Peak Inflow: 01Jan2050, 11:58
Peak Discharge; 213.2 (CFS) Date/Time of Peak Discharge: 01Jan2050r 12:16
Inflow Volume: 6.85 (IN) Peak Storage; 4.3 {AC-FF)
Discharge Volume;6.77 GN) Peak Elevation; 169.6 (FT)
100 year HMS Results at Ash Pond 1985
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