HF Lee CBE - Appendix C_20191230

Wood Environment &Infrastructure Solutions, Inc. wood.
Energy Coal Combustion Residuals Management Program
HF Lee Station Basin CAMA Closure Plan
APPENDIX C — Engineering Evaluations and
Analysis

wood.
March 28, 2019
Mr. Dale Smith
Project Manager
Duke Energy
526 South Church Street
Charlotte, North Carolina 28202
Subject: HF Lee 1982 (Active) Ash Pond H&H Update
Summary of Supporting H&H Analyses
Duke Energy — HF Lee Energy Complex
Wayne County, North Carolina
Wood E&IS Project No. 7812-19-0140
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 HF Lee Energy Complex have sufficient capacity for the design storm with the current outlet
conditions.
Background Information
The former HF Lee Steam Electric Plant was located at 1677 Old Smithfield Road,
approximately 4 miles west of Goldsboro, North Carolina. The plant was sited adjacent to the
Neuse River and formerly hydraulically sluiced ash material into four ash basins: three "Inactive
Basins" west of and across the Neuse River from the plant and one "Active Basin" east of and
across the Neuse River from the plant. The H.F. Lee plant began commercial operations in
1951. The three coal-fired units in the plant were retired in September 2012 followed by the
retirement of four oil -fueled combustion turbine units in October 2012. A natural gas -fired
combined cycle plant started operations in December 2012. Demolition of the plant was
completed in 2017. The HF Lee Steam Plant is permanently retired from service and ash sluice
flow is no longer discharged into the Ash Ponds.
The 1982 (Active) Ash Basin was constructed from September 1978 to April 1980. The Pond
has been used to store coal combustion residuals (CCR) that were sluiced to and deposited into
the holding and settling basin. The materials pumped to the basin primarily consisted of fly ash,
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 HF Lee Plant
March 28, 2019 HF Lee 1982 (Active) Ash Pond H&H Update
Page 2 Wood E&IS Project No. 7812-19-0140
bottom ash, coal slag, unburned coal, and stormwater from the plant. The ash basin is currently
a single perimeter unit, with multiple internal units constructed for basin management and
wastewater treatment.
The HF Lee 1982 (Active) Ash Basin has operated under a National Pollutant Discharge
Elimination System (NPDES) permit number NC0003417 issued by the North Carolina
Department of Environmental Quality (NCDEQ) as a water treatment unit. The basin exterior
embankment is regulated by NCDEQ 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 "HF Lee Active Ash Pond" (State I.D. No. WAYNE-022).
The 1982 (Active) Ash Pond has a surface area of approximately 132 acres, maximum dike
height of approximately 20 feet, crest width of approximately 12 feet, and crest level minimum
Elevation 88.3 feet. The upstream (interior) slope is reported to be 2:1, and the downstream
(exterior) slope is reported to be 2:1.3. The 1982 (Active) Ash Pond has an interior area that
was permitted and used as a "pond within a pond" where an interior dike was constructed on top
of the CCR within the pond and compacted to heights that are above the exterior pond dikes.
This operation was discontinued before reaching the permitted final grades when the plant was
shut down. The interior pond has a small portion that is still under water near its outlet location
to the secondary settling basin of the main pond. The main pond area has a 15-inch RCP
riser/outlet structure that empties into the secondary settling basin; then through a second 42-
inch HDPE discharge pipe that empties into the Neuse River.
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 whether 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 '/z 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 1982 (Active) Ash Pond was obtained from best available reports
and topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation HF Lee Ash
Ponds, McKim and Creed Topographic Survey (2014), LiDAR Topographic Survey by WSP
(2015), and Fleming Engineering, Inc. Bathymetric & Topographic Survey (2018).
The HF Lee 1982 (Active) Ash Pond is 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,

Duke Energy HF Lee Plant
March 28, 2019 HF Lee 1982 (Active) Ash Pond H&H Update
Page 3 Wood E&IS Project No. 7812-19-0140
from the National Oceanic and Atmospheric Administration (Figure 18: All -Season PMP (in.) for
6 hour, 10 mi2) the PMP for the HF Lee site is as follows:
• PMP = 29.49 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 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. 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 structures. The H&H Analyses were conducted for the stage -
storage conditions. The 1982 (Active) Ash Pond has 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. 1982 Ash Pond Outlet Existing Conditions
1982 (Active) Ash Pond
Characteristic
Main Pond
Polishing Pond
Dike Crest Elevation (ft)
88.3
88.3
Culvert Diameter (in)
18
42
Riser/Culvert Elevation (ft)
84.0
81.0
Culvert Material
RCP
HDPE
The settling pond outlets into the Neuse River, and the outlet pipe is in the 100-year floodway and
below the 100-year flood elevation. Thus, the pond discharge will be affected by the river
tailwater. The initial river elevation was assumed to be the 100-year flood elevation of 80.5 feet,
and the river drawdown was estimated using stage data during Hurricane Floyd. The basin is
partially 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
each basin was estimated using the prismatic volume calculation method with the elevation -
surface area input data. Storage volumes for the 1982 (Active) Ash Pond were determined from
contours derived from McKim and Creed Topographic Survey (2014), Fleming Engineering, Inc.

Duke Energy HF Lee Plant
March 28, 2019 HF Lee 1982 (Active) Ash Pond H&H Update
Page 4 Wood E&IS Project No. 7812-19-0140
Bathymetric & Topographic Survey (2018), and WSP LIDAR Topography Survey (2014).
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.
Analysis of the current conditions for the design storm (PMP storm event) in the 1982 (Active)
Ash Pond indicate the basin has the ability to safely contain the design storm (PMP storm event)
and safely pass the inflow volume through the existing discharge structures.
Table 2. Modeling Results
Updated Results
1982 Main Pond
(HydroCAD Pond MP)
1982 Finishing Pond
(HydroCAD Pond FP)
Peak Stage during IDF (ft)
88.2
83.6
Dike Elevation (ft)
88.3
88.3
Pond Freeboard (ft)
0.1
4.7
100% Inflow Volume (acre-ft)
136.1
132.3
80% Inflow Volume (acre-ft)
108.9
105.8
(Minimum) 80% Discharge Time (hr)
160.9
140.7
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 Main Ash Basin safely stores and passes the design storm event, with flow entering the
Finishing Pond. The existing conditions release more than 80% of the inflow to the Main Ash
Basin within 15 days after the design storm begins. The Finishing Pond safely stores and passes
the design storm event, with flow entering the Neuse River. The existing conditions release more
than 80% of the inflow to the Finishing Pond within 15 days after the design storm begins. Thus,

Duke Energy
March 28, 2019
Page 5
HF Lee Plant
HF Lee 1982 (Active) Ash Pond H&H Update
Wood E&IS Project No. 7812-19-0140
the current structures are 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 for the 1982 Ash Basin will safely pass
the design storm (full PMP storm event) without an uncontrolled discharge and meets 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
�q�a��,/yf C50131l P!!D!!
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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: HF Lee Inactive Ash Ponds H&H Update
Summary of Supporting H&H Analyses
Duke Energy — HF Lee Energy Complex
Wayne County, North Carolina
Wood E&IS Project No. 7812-19-0140
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 HF Lee Energy Complex have sufficient capacity for the design storm with the current outlet
conditions.
Background Information
The former HF Lee Steam Electric Plant was located at 1677 Old Smithfield Road,
approximately 4 miles west of Goldsboro, North Carolina. The plant was sited adjacent to the
Neuse River and formerly hydraulically sluiced ash material into four ash basins: three "Inactive
Basins" west of and across the Neuse River from the plant and one "Active Basin" east of and
across the Neuse River from the plant. The H.F. Lee plant began commercial operations in
1951. The three coal-fired units in the plant were retired in September 2012 followed by the
retirement of four oil -fueled combustion turbine units in October 2012. A natural gas -fired
combined cycle plant started operations in December 2012. Demolition of the plant was
completed in 2017. The HF Lee Steam Plant is permanently retired from service and ash sluice
flow is no longer discharged into the Ash Ponds.
The Inactive Ash Ponds 1 and 2 area is located in the northwest corner of the plant site adjacent
to the Neuse River on the east side of the ponds and adjacent to a tributary stream (Halfmile
Branch) to the Neuse on the south side of the ponds. Ash Pond 2 was constructed as an
addition to the east side of Ash Pond 1. From review of limited available descriptive information,
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
HF Lee Plant
HF Lee Inactive Ash Ponds H&H Update
Wood E&IS Project No. 7812-19-0140
these Ash Ponds have a combined available surface area of about 76 acres, estimated
maximum dike height that ranges from 5 to15 feet, and crest width in the range of 14 to 20 feet;
crest level is approximately Elevation 78.5 to 82 feet based on survey data for the site. The
approximate total combined dike length of 11,900 feet (7,700 feet for the exterior dike crest).
The upstream (interior) slope is reported to be in the range of about 2 (horizontal):1 (vertical) to
3 (horizontal):1 (vertical), and the downstream (exterior) slope is reported to be in the range of
1.5 to 2:1. There is a common dike separating the two pond areas; but Pond 1 has no outlet
structure and the two work as a combined pond based on the information found.
The original discharge outlet structure for the combined Ash Ponds 1/2 is located in the
southeast corner and is filled with soil and organic debris. The structure is not functional, and
the outlet could not be located. A secondary retention basin had 2 pipes that formerly exited the
basin (one steel and one RCP) with both emptying to the Neuse River. The steel outlet pipe
was removed in 2015. The RCP riser piping and discharge piping beneath the dike were also
removed in 2015. The Ash Ponds 1/2 area has been inactive since the late 1960s and is
currently dry.
Recent inspection reports indicate the interior of Ash Ponds 1/2 is filled with sedimented ash
which is overgrown by mature trees and brush. The dike slopes are also overgrown with brush
and trees. There is no standing water reported within the Ash Pond area. It is our
understanding that these inactive ponds do not have NPDES permits nor are they regulated
under the NC Dam Safety program (non -jurisdictional) but are on the DENR inventory list as
WAYNE-031 and Wayne-032, respectively.
The Ash Pond 3 area is located south of Ash Ponds 1/2 and is adjacent to the Neuse River
running along the east side of the basin.
From review of limited available descriptive information, this Ash Pond 3 has a surface area of
about 87 acres, estimated maximum dike height in the range of 8 to10 feet, and average crest
width approximately 12 feet; estimated crest level is approximately Elevation 78.5 to 81 feet
based on survey data for the site. The dike length is approximately 8,000 feet. The upstream
(interior) slope is reported to be in the range of 2:1 to 3:1, and the downstream (exterior) slope
is reported to be 2:1 to 3:1.
The original discharge outlet structure for the Ash Pond 3 area was formerly located in the
southeast corner of the pond, was blocked by fill and debris, and was not functional. The riser
structure and discharge pipe beneath the dike were removed in 2015. Recent inspection
reports indicate the interior of the Ash Pond is filled with sedimented ash which is overgrown by
trees and brush. The Ash pond area is dry and has been inactive since about 1980. The south
and west dike areas are inaccessible by vehicle and are covered with thick vegetation and
trees. These areas also have an uneven and inconsistent dike crest. It is our understanding
that this inactive pond does not have NPDES permits nor is regulated under the NC Dam Safety
program (non -jurisdictional) but is listed on the DENR inventory list as WAYNE-033.
H&H Evaluation Criteria
The computer program HydroCAD Version 10.0 was used to perform the H&H calculations to
determine if the current conditions could safely store and pass the revised design storm (full PMP
storm event) without an uncontrolled discharge.

Duke Energy HF Lee Plant
March 28, 2019 HF Lee Inactive Ash Ponds H&H Update
Page 3 Wood E&IS Project No. 7812-19-0140
The existing conditions for the Ash Ponds was obtained from best available reports and
topographic data including the Wood E&IS Hydrologic and Hydraulic Evaluation HF Lee Ash
Ponds, McKim and Creed Topographic Survey (2014), and LiDAR Topographic Survey by WSP
(2015).
The HF Lee Inactive 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 hour,
10 miz) the PMP for the HF Lee site is as follows:
• PMP = 29.49 inches of rainfall for 6 hours
Based on field observations and aerial imagery, the 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 top of ash 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. Additional ponding area details can be found in the modeling
results.
The H&H Analysis was conducted for the proposed stage -storage conditions. There are no outlet
structures in the three Inactive Ash Basins. The H&H Analyses were conducted for the stage -
storage conditions. Wood E&IS assumed a Type II storm distribution for the 6-hr peak
hydrograph.
H&H Summary
Using the information above and the design storm hydrograph, Wood E&IS completed the H&H
Analyses running the models for 240 hours (10 days). Results of the analyses are shown below
in Table 1. The current conditions fail to contain and pass the design storm (PMP storm event)
in all three of the Inactive Ash Basins.
Table 1. Modelina Results
Updated Results
Inactive Ash
Pond 1
(HydroCAD Pond 3P)
Inactive Ash
Pond 2
(HydroCAD Pond 6P)
87.39 (Overtops)
Inactive Ash
Pond 3
(HydroCAD Pond 1 P)
85.40 (Overtops)
Peak Stage during IDF (ft)
82.72 (Overtops)
Dike Elevation (ft)
78.46
78.60
78.13
Pond Freeboard (ft)
-4.26
-8.79
-7.27
100% Inflow Volume (acre-ft)
51.8
79.8
185.2
80% Inflow Volume (acre-ft)
41.4
63.8
148.2
(Minimum) 80% Discharge
Time (hr)
2 9 (87%)
2.7 (94%)
3.9 (86%)

Duke Energy
March 28, 2019
Page 4
HF Lee Plant
HF Lee Inactive Ash Ponds H&H Update
Wood E&IS Project No. 7812-19-0140
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 three Inactive Ash Basins all overtop during the design storm event. The existing conditions
do release over 80% of the inflow within 15 days after the design storm begins. Thus, the current
structures are 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 will not safely store and pass the design
storm (full PMP storm event) without an uncontrolled discharge and will not 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.
lll�Jl�/
William A. Williams, PE, PG
Senior Engineer
Attachments H&H Calculations — HydroCAD Reports
n6g5�9f 45 A 1s 1 rpro"f
11
31zsr..
..
Jeffery Mann, PE
Chief Engineer

4S � 3P
Inactive Pond (1) Inactive Pond (1)
Subca Reach and Lin k
5S
Inactive Pt
(2) Main
4P
Inactive Pod (2) Main
6P � 7S
Inactive Pond (2) Inactive Pond (2)
Finishing Finishing
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HF Leee Inactive Ponds 1and2
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 2
Area Listing (all nodes)
Area CN Description
(acres) (subcatchment-numbers)
75.920 73 Woods, Fair, HSG C (4S, 5S, 7S)
75.920 73 TOTAL AREA
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HF Leee Inactive Ponds 1and2
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 3
Soil Listing (all nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000
HSG A
0.000
HSG B
75.920
HSG C 4S, 5S, 7S
0.000
HSG D
0.000
Other
75.920
TOTAL AREA
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCADO 10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 4
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Subcatchment 4S: Inactive Pond (1) Runoff Area=24.405 ac 0.00% Impervious Runoff Depth=25.47"
Flow Length=1,949' Tc=157.8 min CN=73 Runoff=210.71 cfs 51.806 of
Subcatchment 5S: Inactive Pond (2) Main Runoff Area=49.564 ac 0.00% Impervious Runoff Depth=25.47"
Flow Length=1,448' Tc=116.7 min CN=73 Runoff=543.69 cfs 105.213 of
Subcatchment 7S: Inactive Pond (2) Finishing Runoff Area=1.951 ac 0.00% Impervious Runoff Depth=25.47"
Flow Length=256' Tc=21.6 min CN=73 Runoff=69.43 cfs 4.142 of
Pond 3P: Inactive Pond (1)
Peak Elev=82.72' Storage=545,884 cf Inflow=210.71 cfs 51.806 of
Outflow=231.09 cfs 45.334 of
Pond 4P: Inactive Pond (2) Main Peak Elev=83.89' Storage=31.269 of Inflow=543.69 cfs 105.213 of
Primary=743.96 cfs 75.663 of Secondary=321.02 cfs 15.259 of Outflow=764.72 cfs 90.923 of
Pond 6P: Inactive Pond (2) Finishing Peak Elev=87.39' Storage=6.515 of Inflow=749.14 cfs 79.805 of
Outflow=743.98 cfs 74.858 of
Total Runoff Area = 75.920 ac Runoff Volume=161.161 of Average Runoff Depth = 25.47"
100.00% Pervious = 75.920 ac 0.00% Impervious = 0.000 ac
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 5
Summary for Subcatchment 4S: Inactive Pond (1)
Runoff = 210.71 cfs @ 4.89 hrs, Volume= 51.806 af, Depth=25.47"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 6-hr PMP Rainfall=29.49"
Area (ac) CN Description
24.405 73 Woods, Fair, HSG C
24.405 100.00% Pervious Area
Tc Length
Slope
Velocity Capacity
Description
(min) (feet)
(ft/ft)
(ft/sec) (cfs)
26.4 100
0.0100
0.06
Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.68"
131.4 1,849
0.0022
0.23
Shallow Concentrated Flow,
Woodland Kv= 5.0 fDs
157.8 1,949 Total
1 210.71 cfs I
200
180
160
140
3 120
2 100
80
60
40
20
0
Subcatchment 4S: Inactive Pond (1)
Hydrograph
Type II
6-hr
PMP Rainfall=29.49"
Runoff Area=24.405 ac
Runoff Volume=51.806 of
Runoff Pepth=25 47"
-------- Flow _Length _=1.949'
Tc=1 v7.8 min
CN=73
0 20 40 60 80 100 120 140 160 180 200 220 240
Time (hours)
0 Runoff
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 6
Summary for Subcatchment 5S: Inactive Pond (2) Main
Runoff = 543.69 cfs @ 4.31 hrs, Volume= 105.213 af, Depth=25.47"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 6-hr PMP Rainfall=29.49"
Area (ac) CN Description
49.564 73 Woods, Fair, HSG C
49.564 100.00% Pervious Area
Tc Length
Slope
Velocity Capacity
Description
(min) (feet)
(ft/ft)
(ft/sec) (cfs)
42.8 100
0.0030
0.04
Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.68"
73.9 1,348
0.0037
0.30
Shallow Concentrated Flow,
Woodland Kv= 5.0 fDs
116.7 1,448 Total
Subcatchment 5S: Inactive Pond (2) Main
Hydrograph
543.69 cfs550
--------------
-
-- -- -- -- -: - --.Type.-11
,
500
6-hr
-
450
PIMP Rainfall=2949"
400
Runoff Area=49.564 ac
=
Runoff Volume_ p5.21 3 of350
300
De th-2547 ; .,
p
R'
3
0
FL 250
{' Flow=
LTc g116448'
- - min
200
-- -- -- --!- -- CN!=73
150
----------
100
50
0
0 20
40 60 80 100 120 140 160 180 200 220 240
Time (hours)
0 Runoff
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 7
Summary for Subcatchment 7S: Inactive Pond (2) Finishing
Runoff = 69.43 cfs @ 3.14 hrs, Volume= 4.142 af, Depth=25.47"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 6-hr PMP Rainfall=29.49"
Area (ac) CN Description
1.951 73 Woods, Fair, HSG C
1.951 100.00% Pervious Area
Tc Length
(min) (feet)
Slope
(ft/ft)
Velocity Capacity
(ft/sec) (cfs)
Description
17.0 100
0.0300
0.10
Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.68"
4.6 156
0.0128
0.57
Shallow Concentrated Flow,
Woodland Kv= 5.0 fDs
21.6 256 Total
Subcatchment 7S: Inactive Pond (2) Finishing
Hydrograph
1 69.43 cfs I'
60
�. 50
40
3
0
FL 30
20
1
Type 11
----6-hr
PMP Rainfall=29.49"
Runoff A rea=1.951 ac
Runoff Volume=4.142 of
Runoff Depth=25.47"
Flow, Length=256'
Tc=21.6 min
CN=73
0 20 40 60 80 100 120 140 160 180 200 220 240
Time (hours)
0 Runoff
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 8
Summary for Pond 3P: Inactive Pond (1)
[93] Warning: Storage range exceeded by 3.72'
[90] Warning: Qout>Qin may require smaller dt or Finer Routing
[87] Warning: Oscillations may require smaller dt or Finer Routing (severity=45)
Inflow Area = 24.405 ac, 0.00% Impervious, Inflow Depth = 25.47" for PMP event
Inflow = 210.71 cfs @ 4.89 hrs, Volume= 51.806 of
Outflow = 231.09 cfs @ 4.90 hrs, Volume= 45.334 af, Atten= 0%, Lag= 0.5 min
Primary = 231.09 cfs @ 4.90 hrs, Volume= 45.334 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 82.72' @ 4.90 hrs Surf.Area= 576,949 sf Storage= 545,884 cf
Plug -Flow detention time= 171.7 min calculated for 45.324 of (87% of inflow)
Center -of -Mass det. time= 150.4 min (483.2 - 332.7 )
Volume Invert Avail.Storage Storage Description
#1 77.00' 545,884 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
77.00 7,241 0 0
78.00 253,789 130,515 130,515
79.00 576,949 415,369 545,884
Device Routing Invert Outlet Devices
#1 Primary 78.46' 10.0' long x 20.0' breadth Broad -Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
PrimaryOutFlow Max=231.03 cfs @ 4.90 hrs HW=82.72' (Free Discharge)
L1=Broad-Crested Rectangular Weir (Weir Controls 231.03 cfs @ 5.43 fps)
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 9
Inflow
❑ Primary
1 .........1
1 1 41 •:1 111 1 1 1 1•1 1:1 211 220 240
Time (hours)
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 10
Summary for Pond 4P: Inactive Pond (2) Main
[93] Warning: Storage range exceeded by 4.89'
[95] Warning: Outlet Device #1 rise exceeded
[90] Warning: Qout>Qin may require smaller dt or Finer Routing
[87] Warning: Oscillations may require smaller dt or Finer Routing (severity=67)
Inflow Area = 49.564 ac, 0.00% Impervious, Inflow Depth = 25.47" for PMP event
Inflow = 543.69 cfs @ 4.31 hrs, Volume= 105.213 of
Outflow = 764.72 cfs @ 4.30 hrs, Volume= 90.923 af, Atten= 0%, Lag= 0.0 min
Primary = 743.96 cfs @ 4.30 hrs, Volume= 75.663 of
Secondary = 321.02 cfs @ 4.35 hrs, Volume= 15.259 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 83.89' @ 4.35 hrs Surf.Area= 28.777 ac Storage= 31.269 of
Plug -Flow detention time= 218.2 min calculated for 90.904 of (86% of inflow)
Center -of -Mass det. time= 199.5 min (493.7 - 294.2 )
Volume Invert Avail.Storage Storage Description
#1 75.00' 31.269 of Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (acres) (acre-feet) (acre-feet)
75.00 0.032 0.000 0.000
76.00 0.718 0.375 0.375
77.00 3.452 2.085 2.460
78.00 12.695 8.073 10.533
79.00 28.777 20.736 31.269
Device Routing Invert Outlet Devices
#1 Primary 78.24' Asymmetrical Weir, C= 3.27
Offset (feet) 0.00 23.67 50.16 78.18 105.26 132.38 161.05 188.58
216.21 243.84 270.28 296.76 325.38 352.74 379.86 407.17 434.48
460.89 486.88 514.56 542.39 568.81 596.89
Height (feet) 4.44 4.44 4.44 4.44 4.31 4.24 4.35 4.26 4.16 3.91
3.58 3.72 3.93 3.70 3.69 3.81 3.76 3.39 3.24 3.53 3.89 4.22 4.44
#2 Secondary 78.60' 10.0' long x 10.0' breadth Broad -Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=0.00 cfs @ 4.30 hrs HW=79.44' TW=87.39' (Dynamic Tailwater)
L1=Asymmetrical Weir ( Controls 0.00 cfs)
Secondary OutFlow Max=321.02 cfs @ 4.35 hrs HW=83.89' (Free Discharge)
L2=Broad-Crested Rectangular Weir (Weir Controls 321.02 cfs @ 6.07 fps)
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 11
Pond 4P: Inactive Pond (2) Main
Hydrograph
----------- [ Inflow
s--------
- .564 ac Outflow
743.96 cf now rea-
Peak Elev=83.89' El Primary
5 9 cfs g = of Secondary
700
Stora a=31.269
600
500
0 321.02 cfs
" 300
200
100
0
0 20 40 60 80 100120 140 160 180 200 220 240
Time (hours)
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 12
Summary for Pond 6P: Inactive Pond (2) Finishing
[93] Warning: Storage range exceeded by 8.39'
[80] Warning: Exceeded Pond 4P by 7.95' @ 4.30 hrs (3,836.85 cfs 443.509 af)
Inflow Area =
51.515 ac,
0.00% Impervious, Inflow Depth = 18.59" for PMP event
Inflow =
749.14 cfs @
4.30 hrs, Volume= 79.805 of
Outflow =
743.98 cfs @
4.30 hrs, Volume= 74.858 af, Atten= 1%, Lag= 0.0 min
Primary =
743.98 cfs @
4.30 hrs, Volume= 74.858 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 87.39' @ 4.30 hrs
Surf.Area= 1.951 ac Storage= 6.515 of
Plug -Flow detention time= 163.3
min calculated for 74.842 of (94% of inflow)
Center -of -Mass det. time= 44.1
min ( 552.9 - 508.7 )
Volume
Invert Avail.Storage Storage Description
#1
73.00' 6.515 of Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store Cum.Store
(feet)
(acres)
(acre-feet) (acre-feet)
73.00
0.039
0.000 0.000
74.00
0.514
0.276 0.276
75.00
0.846
0.680 0.956
76.00
1.131
0.988 1.945
77.00
1.396
1.263 3.209
78.00
1.633
1.514 4.723
79.00
1.951
1.792 6.515
Device Routina Invert Outlet Devices
#1 Primary 78.13' 10.0' long x 10.0' breadth Broad -Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=743.98 cfs @ 4.30 hrs HW=87.39' (Free Discharge)
L1=113road-Crested Rectangular Weir (Weir Controls 743.98 cfs @ 8.03 fps)
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HF Leee Inactive Ponds 1and2 Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 13
Pond 6P: Inactive Pond (2) Finishing
Hydrograph
1 743.98 cfs f
700
600
500
0 400
" 300
200
100
0
0
Inflow
Inflow Area=51.315' ac ❑Primary
Peak Elev^87.39'
Storage=6.515 of
20 40 60 80 100 120 140 160 180 200 220 240
Time (hours)
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2S )>
Pond 3 Area
Subca Reach and Lin k
Inactive Pond (3)
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HF Lee Inactive Pond3 Only
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 2
Area Listing (all nodes)
Area CN Description
(acres) (subcatchment-numbers)
87.267 73 Woods, Fair, HSG C (2S)
87.267 73 TOTAL AREA
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HF Lee Inactive Pond3 Only
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 3
Soil Listing (all nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000
HSG A
0.000
HSG B
87.267
HSG C 2S
0.000
HSG D
0.000
Other
87.267
TOTAL AREA
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HF Lee Inactive Pond3 Only Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 4
Time span=0.00-240.00 hrs, dt=0.05 hrs, 4801 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Subcatchment 2S: Pond 3 Area Runoff Area=87.267 ac 0.00% Impervious Runoff Depth=25.47"
Flow Length=2,364' Tc=169.8 min CN=73 Runoff=714.03 cfs 185.248 of
Pond 1P: Inactive Pond (3) Peak Elev=85.40' Storage=2,938,156 cf Inflow=714.03 cfs 185.248 of
Outflow= 1, 1 52.98cfs 158.590 of
Total Runoff Area = 87.267 ac Runoff Volume=185.248 of Average Runoff Depth = 25.47"
100.00% Pervious = 87.267 ac 0.00% Impervious = 0.000 ac
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HF Lee Inactive Pond3 Only Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 5
Summary for Subcatchment 2S: Pond 3 Area
Runoff = 714.03 cfs @ 5.07 hrs, Volume= 185.248 af, Depth=25.47"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Type II 6-hr PMP Rainfall=29.49"
Area (ac) CN Description
87.267 73 Woods, Fair, HSG C
87.267 100.00% Pervious Area
Tc
Length
Slope
Velocity Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec) (cfs)
34.9
100
0.0050
0.05
Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.68"
129.2
1,899
0.0024
0.24
Shallow Concentrated Flow,
Woodland Kv= 5.0 fps
5.7
365
0.0082
1.06 38.15
Channel Flow,
Area= 36.0 sf Perim= 72.0' r= 0.50'
n= 0.080 Earth. Iona dense weeds
169.8 2,364 Total
Subcatchment 2S: Pond 3 Area
Hydrograph
714.03
cfs
700
Type II
.6-hr
600
PMP Rainfall=2949"
Runoff Area=87.267 ac
^ 500
Runoff Volume=185.248 of
400
Runoff, Depth=2547"
3
o
Flow Length=2,364'
u- 300
Tc=1'69.8'min
C N',=73
200
100
1 20 41 .1 81 100 120 140 160 180 200 220 240
Time (hours)
Runoff
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HF Lee Inactive Pond3 Only Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 © 2018 HydroCAD Software Solutions LLC Page 6
Summary for Pond 1 P: Inactive Pond (3)
[93] Warning: Storage range exceeded by 6.40'
[90] Warning: Qout>Qin may require smaller dt or Finer Routing
[87] Warning: Oscillations may require smaller dt or Finer Routing (severity=33)
Inflow Area =
87.267 ac,
0.00% Impervious, Inflow Depth = 25.47" for PMP event
Inflow =
714.03 cfs @
5.07 hrs, Volume= 185.248 of
Outflow =
1,152.98 cfs @
5.10 hrs, Volume= 158.590 af, Atten= 0%, Lag= 1.9 min
Primary =
1,152.98 cfs @
5.10 hrs, Volume= 158.590 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-240.00 hrs, dt= 0.05 hrs
Peak Elev= 85.40' @ 5.10 hrs
Surf.Area= 1,868,520 sf Storage= 2,938,156 cf
Plug -Flow detention time= 234.5
min calculated for 158.557 of (86% of inflow)
Center -of -Mass det. time= 209.1
min ( 551.4 - 342.4 )
Volume
Invert Avail.Storage Storage Description
#1
74.00' 2,938,156 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store Cum.Store
(feet)
(sq-ft)
(cubic -feet) (cubic -feet)
74.00
43,917
0 0
75.00
173,224
108,571 108,571
76.00
302,215
237,720 346,290
77.00
539,790
421,003 767,293
78.00
966,708
753,249 1,520,542
79.00
1,868,520
1,417,614 2,938,156
Device Routina Invert Outlet Devices
#1 Primary 77.59' 20.0' long x 10.0' breadth Broad -Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max=1,152.98 cfs @ 5.10 hrs HW=85.40' (Free Discharge)
L1=Broad-Crested Rectangular Weir (Weir Controls 1,152.98 cfs @ 7.38 fps)
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HF Lee Inactive Pond3 Only Type/1 6-hr PMP Rainfall=29.49"
Prepared by AMECFW Printed 3/14/2019
HydroCAD®10.00-23 s/n 01035 ©2018 HydroCAD Software Solutions LLC Page 7
Pond 1 P: Inactive Pond (3)
Hydrograph
Inflow
1,152.98 cfs ❑ Primary
Inflow: Area=87.267;ac
p eak Elev=85.40'
1,000 Storage=2,938,156 cf
71 3 cfs
8
0 600
FL
400
200
1 1 41 61 81 100 120 140 160 180 200 220 240
Time (hours)
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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
HF Lee Energy Complex Ash Basin Decommissioning
Duke Energy — HF Lee Steam Station
Wayne County, North Carolina
Wood Project No. 7812180091
Dear Mr. Smith,
As part of the decommissioning plan for the HF Lee Ash Basins, Wood Environment &
Infrastructure Solutions, Inc. (Wood) has prepared this Hydraulic and Hydrologic analysis (H&H)
summary report. This H&H summary represents the HF Lee Ash Basins in the proposed
decommissioned condition.
Background Information
The former HF Lee Steam Electric Plant was located at 1677 Old Smithfield Road, approximately
4 miles west of Goldsboro, North Carolina. The plant was sited adjacent to the Neuse River and
formerly hydraulically sluiced ash material into four ash basins: three "Inactive Basins" west of
and across the Neuse River from the plant and one "Active Basin" east of and across the Neuse
River from the plant. The H.F. Lee plant began commercial operations in 1951. The three coal-
fired units in the plant were retired in September 2012 followed by the retirement of four oil -fueled
combustion turbine units in October 2012. A natural gas -fired combined cycle plant started
operations in December 2012. Demolition of the plant was completed in 2017. The HF Lee
Steam Plant is permanently retired from service and ash sluice flow is no longer discharged into
the Ash Ponds.
The Inactive Ash Ponds 1 and 2 area is located in the northwest corner of the plant site adjacent
to the Neuse River on the east side of the ponds and adjacent to a tributary stream (Halfmile
Branch) to the Neuse on the south side of the ponds. Ash Pond 2 was constructed as an addition
to the east side of Ash Pond 1. From review of limited available descriptive information, these
Ash Ponds have a combined available surface area of about 76 acres, estimated maximum dike
height that ranges from 5 to15 feet, and crest width in the range of 14 to 20 feet; crest level is
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Tel [phone]
Fax [phone]
www.woodi)lc.com
Licensure: NC Engineering F-1253 NC Geology C-247

Duke Energy HF Lee Energy Complex
October 11, 2019 Hydrology and Hydraulics Analysis Summary Report
Page 2 Wood Project No. 7812180091
approximately Elevation 78.5 to 82 feet based on survey data for the site. The approximate total
combined dike length of 11,900 feet (7,700 feet for the exterior dike crest). The upstream (interior)
slope is reported to be in the range of about 2 (horizontal):1 (vertical) to 3 (horizontal):1 (vertical),
and the downstream (exterior) slope is reported to be in the range of 1.5 to 2:1. There is a
common dike separating the two pond areas; but Pond 1 has no outlet structure and the two work
as a combined pond based on the information found.
The original discharge outlet structure for the combined Ash Ponds 1/2 is located in the southeast
corner and is filled with soil and organic debris. The structure is not functional, and the outlet
could not be located. A secondary retention basin had 2 pipes that formerly exited the basin (one
steel and one RCP) with both emptying to the Neuse River. The steel outlet pipe was removed
in 2015. The RCP riser piping and discharge piping beneath the dike were also removed in 2015.
The Ash Ponds 1/2 area has been inactive since the late 1960s and is currently dry.
Recent inspection reports indicate the interior of Ash Ponds 1/2 is filled with sedimented ash which
is overgrown by mature trees and brush. The dike slopes are also overgrown with brush and
trees. There is no standing water reported within the Ash Pond area. It is our understanding that
these inactive ponds do not have NPDES permits nor are they regulated under the NC Dam
Safety program (non -jurisdictional) but are on the DENR inventory list as WAYNE-031 and
Wayne-032, respectively.
The Ash Pond 3 area is located south of Ash Ponds 1/2 and is adjacent to the Neuse River running
along the east side of the basin.
From review of limited available descriptive information, this Ash Pond 3 has a surface area of
about 87 acres, estimated maximum dike height in the range of 8 to10 feet, and average crest
width approximately 12 feet; estimated crest level is approximately Elevation 78.5 to 81 feet based
on survey data for the site. The dike length is approximately 8,000 feet. The upstream (interior)
slope is reported to be in the range of 2:1 to 3:1, and the downstream (exterior) slope is reported
to be 2:1 to 3:1.
The original discharge outlet structure for the Ash Pond 3 area was formerly located in the
southeast corner of the pond, was blocked by fill and debris, and was not functional. The riser
structure and discharge pipe beneath the dike were removed in 2015. Recent inspection reports
indicate the interior of the Ash Pond is filled with sedimented ash which is overgrown by trees and
brush. The Ash pond area is dry and has been inactive since about 1980. The south and west
dike areas are inaccessible by vehicle and are covered with thick vegetation and trees. These
areas also have an uneven and inconsistent dike crest. It is our understanding that this inactive
pond does not have NPDES permits nor is regulated under the NC Dam Safety program (non -
jurisdictional) but is listed on the DENR inventory list as WAYNE-033.
H&H Evaluation Criteria
The computer program HydroCAD 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.

Duke Energy HF Lee Energy Complex
October 11, 2019 Hydrology and Hydraulics Analysis Summary Report
Page 3 Wood Project No. 7812180091
The 1982 Active 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 550 feet wide, cut to an elevation of 70 feet.
The Inactive Ash Basins 1 and 2, in the decommissioned conditions, will consist of the basin dikes
with an opening (breach) in the eastern dike section. The dike opening is designed to be
approximately 100 feet wide, cut to an elevation of 72 feet.
The Inactive Ash Basin 3, in the decommissioned conditions, will consist of the basin dikes with
an opening (breach) in the northern dike section. The dike opening is designed to be
approximately 100 feet wide, cut to an elevation of 72 feet.
The HF Lee Ash Ponds design storm for the decommissioned condition is the 100-year storm
event, which equates to 9.59 inches of rainfall for a twenty four (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
1982 Active
Ash Basin
Inactive Basin 1/2
Inactive Basin 3
Peak Water Elevation (ft)
71.96
73.96
71.94
Weir (Opening) Elevation (ft)
70
72
70
Dike Crest Elevation (ft)
88.3
78.5
77.6
Pond Freeboard (ft)
16.34
4.54
5.66
Peak Discharge Rate (ft3/s)
966.25
683.59
925.8
Peak Velocity (ft/s)
3.77
0.63
4.51

Duke Energy
October 11, 2019
Page 4
Conclusion
HF Lee Energy Complex
Hydrology and Hydraulics Analysis Summary Report
Wood Project No. 7812180091
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,
Woo i C lton R,ent & Infrastructure Solutions, Inc.
AL
8229 3
Adam Pilarz, PE
Civil Manager
Attachments H&H Calculation — Decommissioned Conditions

1S
1982 Activt sh Basin
1R
AB Breac Channel
1L
2S
Inactive At Basin 1/2
2R
Inactive Ba in 1 Breach
C nel
2L
Outlet
Outlet
Subcat Reach on Link
4S
Inactive A h Basin 3
4R
Inactive Ba in 3 Breach
Ch nnel
4L
Outlet

HF Lee CAMA Closure Breach
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 2
Area Listing (all nodes)
Area CN Description
(acres) (subcatchment-numbers)
131.860 88 Newly Graded Areas (1S)
162.140 90 Newly Graded Areas (2S, 4S)
294.000 89 TOTAL AREA

HF Lee CAMA Closure Breach
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 3
Soil Listing (all nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000
HSG A
0.000
HSG B
0.000
HSG C
0.000
HSG D
294.000
Other 1 S, 2S, 4S
294.000
TOTAL AREA

HF Lee CAMA Closure Breach
Prepared by AMECFW Printed 10/11/2019
HydroCAD® 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 4
Ground Covers (all nodes)
HSG-A HSG-B HSG-C HSG-D Other Total Ground Subcatchment
(acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers
0.000 0.000 0.000 0.000 294.000 294.000 Newly Graded Areas 1 S, 2S, 4S
0.000 0.000 0.000 0.000 294.000 294.000 TOTAL AREA

HF Lee CAMA Closure Breach Type 1l 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCAD® 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 5
Time span=0.00-95.00 hrs, dt=0.01 hrs, 9501 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Subcatchment 1 S: 1982 Active Ash Basin Runoff Area=131.860 ac 0.00% Impervious Runoff Depth=8.13"
Flow Length=2,700' Slope=0.0100 '/' Tc=43.6 min CN=88
Runoff=966.87 cfs 89.310 of
Subcatchment2S: Inactive Ash Basin 1/2 Runoff Area=75.490 ac 0.00% Impervious
Runoff Depth=8.37"
Flow Length=2,800' Slope=0.0100 '/' Tc=29.5 min CN=90
Runoff=732.87 cfs 52.682 of
Subcatchment4S: Inactive Ash Basin 3 Runoff Area=86.650 ac 0.00% Impervious
Runoff Depth=8.37"
Flow Length=2,380' Slope=0.0100 T Tc=25.1 min CN=90
Runoff=929.22 cfs 60.471 of
Reach 1 R: AB Breach Channel Avg. Flow Depth=1.96' Max Vet=3.77 fps
Inflow=966.87 cfs 89.310 of
n=0.069 L=150.0' S=0.0133 '/' Capacity=1,982.26 cfs
Outflow=966.25 cfs 89.310 of
Reach 2R: Inactive Basin 1 Breach Avg. Flow Depth=1.96' Max Vet=0.63 fps
Inflow=732.87 cfs 52.682 of
n=0.069 L=285.0' S=0.0004 '/' Capacity=1,390.72 cfs
Outflow=683.59 cfs 52.682 of
Reach 4R: Inactive Basin 3 Breach Avg. Flow Depth=1.94' Max Vet=4.51 fps
Inflow=929.22 cfs 60.471 of
n=0.069 L=102.0' S=0.0196 '/' Capacity=1,934.92 cfs
Outflow=928.80 cfs 60.471 of
Link 1 L: Outlet
Link 2L: Outlet
Link 4L: Outlet
Inflow=966.25 cfs 89.310 of
Primary=966.25 cfs 89.310 of
Inflow=683.59 cfs 52.682 of
Primary=683.59 cfs 52.682 of
Inflow=928.80 cfs 60.471 of
Primary=928.80 cfs 60.471 of
Total Runoff Area = 294.000 ac Runoff Volume = 202.463 of Average Runoff Depth = 8.26"
100.00% Pervious = 294.000 ac 0.00% Impervious = 0.000 ac

HF Lee CAMA Closure Breach Type/1 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 6
Summary for Subcatchment 1S: 1982 Active Ash Basin
Runoff = 966.87 cfs @ 3.39 hrs, Volume= 89.310 af, Depth= 8.13"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Type II 6-hr 100-yr 24-hr Rainfall=9.59"
Area (ac) CN Description
131.860 88 Newly Graded Areas
131.860 100.00% Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
3.6 300
0.0100
1.39
Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.69"
40.0 2,400
0.0100
1.00
Shallow Concentrated Flow,
Nearlv Bare & Untilled Kv= 10.0 fps
43.6 2,700 Total
800
700
600
0 500
400
300
200
100
0
Subcatchment 1S: 1982 Active Ash Basin
Hydrograph
�I
t L
I-
A L I —1 ITjpel u
�� 6- r
100-yr 24I hrRainfall=9.5 "
--2ui�of Ariea=13-�F.860 ad
Rrr Yolume= 40 f
—Ru-noff De = .l
FI%w te6gth=2 700'
Slope- 0I­M
00 I'/'
I— W3.in
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time (hours)
0 Runoff

HF Lee CAMA Closure Breach Type/1 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 7
Summary for Subcatchment 2S: Inactive Ash Basin 1/2
Runoff = 732.87 cfs @ 3.22 hrs, Volume= 52.682 af, Depth= 8.37"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Type II 6-hr 100-yr 24-hr Rainfall=9.59"
Area (ac) CN Description
75.490 90 Newly Graded Areas
75.490 100.00% Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
3.6 300
0.0100
1.39
Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.69"
25.9 2,500
0.0100
1.61
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
29.5 2,800 Total
Subcatchment 2S: Inactive Ash Basin 1/2
Hydrograph
732.87 cfs
-4
4
700
J
600
N 500
t/
3
-1
L
3 400
0
" 300
200
100
Type II
l 6 r
100 yr 2 hr Rainfall 9.5 "
-Runoff Area--75.490-at
�uoVolurea2e.fg.f�ff
1Pth-uno Fjovv I-Ongth=2,800'
c= 9. min
I CN=$O
1,
0
5 10 15 20 25 30 35 4041 55 60. 1 75 80 85 90 95
0 Runoff

HF Lee CAMA Closure Breach Type/1 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 8
Summary for Subcatchment 4S: Inactive Ash Basin 3
Runoff = 929.22 cfs @ 3.18 hrs, Volume= 60.471 af, Depth= 8.37"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Type II 6-hr 100-yr 24-hr Rainfall=9.59"
Area (ac) CN Description
86.650 90 Newly Graded Areas
86.650 100.00% Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
3.6 300
0.0100
1.39
Sheet Flow,
Smooth surfaces n= 0.011 P2= 3.69"
21.5 2,080
0.0100
1.61
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
25.1 2,380 Total
3
3
0
FL
929.22 cfs
900
800
700
600
500
400
300
200
100
0
0
Subcatchment 4S: Inactive Ash Basin 3
Hydrograph
T T T T ITT I T tTypel
T T7 T T
T I T T
-F T I T T
1-yr24lJir R�nfall=2�5 "
R6n4f A'►re�=8�.6�0 ac
Rroff Yolnp=f0.471 f
—Rurfoff De " "
TFIiwv Lengt4=2,380'
Slope=1-15.1
000'/'
�1 c= min
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time (hours)
0 Runoff

HF Lee CAMA Closure Breach Type 11 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 9
Summary for Reach 1 R: AB Breach Channel
Inflow Area = 131.860 ac, 0.00% Impervious, Inflow Depth = 8.13" for 100-yr 24-hr event
Inflow = 966.87 cfs @ 3.39 hrs, Volume= 89.310 of
Outflow = 966.25 cfs @ 3.40 hrs, Volume= 89.31Oaf, Atten= 0%, Lag= 0.5 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Max. Velocity= 3.77 fps, Min. Travel Time= 0.7 min
Avg. Velocity = 1.16 fps, Avg. Travel Time= 2.2 min
Peak Storage= 38,453 cf @ 3.40 hrs
Average Depth at Peak Storage= 1.96'
Bank -Full Depth= 3.00' Flow Area= 402.0 sf, Capacity= 1,982.26 cfs
125.00' x 3.00' deep channel, n= 0.069 Riprap, 6-inch
Side Slope Z-value= 3.0 7' Top Width= 143.00'
Length= 150.0' Slope= 0.0133 7'
Inlet Invert= 75.00', Outlet Invert= 73.00'
Reach 1 R: AB Breach Channel
Hydrograph
•OSI■
... �� :.
900
a Max
:11 77 fps
%� 1 1.•
11 j j
• 11 ,
500
300
11 i� j
1 1 1 1 �1� 1 •1 • 1 :1 : •1 •
❑ Inflow
❑ Outflow

HF Lee CAMA Closure Breach Type 11 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 10
Summary for Reach 2R: Inactive Basin 1 Breach Channel
Inflow Area = 75.490 ac, 0.00% Impervious, Inflow Depth = 8.37" for 100-yr 24-hr event
Inflow = 732.87 cfs @ 3.22 hrs, Volume= 52.682 of
Outflow = 683.59 cfs @ 3.31 hrs, Volume= 52.682 af, Atten= 7%, Lag= 5.1 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Max. Velocity= 0.63 fps, Min. Travel Time= 7.6 min
Avg. Velocity = 0.08 fps, Avg. Travel Time= 61.1 min
Peak Storage= 310,659 cf @ 3.31 hrs
Average Depth at Peak Storage= 1.96'
Bank -Full Depth= 3.00' Flow Area= 1,677.0 sf, Capacity= 1,390.72 cfs
550.00' x 3.00' deep channel, n= 0.069 Riprap, 6-inch
Side Slope Z-value= 3.0 '/' Top Width= 568.00'
Length= 285.0' Slope= 0.0004 '/'
Inlet Invert= 73.10', Outlet Invert= 73.00'
Reach 2R: Inactive Basin 1 Breach Channel
Hydrograph
732.87 cfs +
683.59 cfs Inflow Area=75.490 ac
Avg. Flow Depth=1.96'
600 Max Vet=0.63 fps
n=0.069
500 L=285.0'
3 400 S=0.0004 '/'
o Capacity=1,390.72 cfs
v__ 300
200
100
1 ►�.iiiiii...........
0 1 1 1 4041 ...........
1 :1: 90•
❑ Inflow
❑ Outflow

HF Lee CAMA Closure Breach Type/1 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 11
Summary for Reach 4R: Inactive Basin 3 Breach Channel
Inflow Area = 86.650 ac, 0.00% Impervious, Inflow Depth = 8.37" for 100-yr 24-hr event
Inflow = 929.22 cfs @ 3.18 hrs, Volume= 60.471 of
Outflow = 928.80 cfs @ 3.18 hrs, Volume= 60.471 af, Atten= 0%, Lag= 0.1 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Max. Velocity= 4.51 fps, Min. Travel Time= 0.4 min
Avg. Velocity = 1.39 fps, Avg. Travel Time= 1.2 min
Peak Storage= 20,983 cf @ 3.18 hrs
Average Depth at Peak Storage= 1.94'
Bank -Full Depth= 3.00' Flow Area= 327.0 sf, Capacity= 1,934.92 cfs
100.00' x 3.00' deep channel, n= 0.069 Riprap, 6-inch
Side Slope Z-value= 3.0 7' Top Width= 118.00'
Length= 102.0' Slope= 0.0196 T
Inlet Invert= 72.00', Outlet Invert= 70.00'
3
0
FL
Reach 4R: Inactive Basin 3 Breach Channel
928.80 cfs P.
900
800
700
600
500
400
300
200
100
0
0
Hydrograph
—I ­4 -t-- I — I rt �
I TIn1flo"rc_a=k650 ac
I Ayq.1 H1 w-1101�pth=1.94`
MaxVel=4.51, fps
1 1 1 1 1 1=
�' o.o69-
L�lg1p�
S=0.01 6 T
fiClapa�y�,�34.9 c�S-
i i i i l l l l l l
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time (hours)
Inflow
❑ Outflow

HF Lee CAMA Closure Breach Type 11 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 12
Summary for Link 1 L: Outlet
Inflow Area = 131.860 ac, 0.00% Impervious, Inflow Depth = 8.13" for 100-yr 24-hr event
Inflow = 966.25 cfs @ 3.40 hrs, Volume= 89.310 of
Primary = 966.25 cfs @ 3.40 hrs, Volume= 89.31Oaf, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
3
0
FL
300
200
100
0
Link 1 L: Outlet
Hydrograph
0 5 1015 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time (hours)
❑ Inflow
❑ Primary

HF Lee CAMA Closure Breach Type 11 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 13
Summary for Link 2L: Outlet
Inflow Area = 75.490 ac, 0.00% Impervious, Inflow Depth = 8.37" for 100-yr 24-hr event
Inflow = 683.59 cfs @ 3.31 hrs, Volume= 52.682 of
Primary = 683.59 cfs @ 3.31 hrs, Volume= 52.682 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
Link 2L: Outlet
Hydrograph
I I ❑ Inflow
683.5rds El Primary
Wlo�v Area=� 5.490 ac
600
o
11
• j
FL /' I
alff
60 65 70 75 80 85 90 •

HF Lee CAMA Closure Breach Type/1 6-hr 100-yr 24-hr Rainfall=9.59"
Prepared by AMECFW Printed 10/11/2019
HydroCADO 10.00-25 s/n 01035 © 2019 HydroCAD Software Solutions LLC Page 14
Summary for Link 4L: Outlet
Inflow Area = 86.650 ac, 0.00% Impervious, Inflow Depth = 8.37" for 100-yr 24-hr event
Inflow = 928.80 cfs @ 3.18 hrs, Volume= 60.471 of
Primary = 928.80 cfs @ 3.18 hrs, Volume= 60.471 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-95.00 hrs, dt= 0.01 hrs
3
3
0
FZ
I
Link 4L: Outlet
Hydrograph
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Time (hours)
Inflow
❑ Primary