20231101 Ver 1_More Info Received_20240426 (3)

April 26, 2024
Delivered via email to: BrookeA.Davis(@.usace.army.mil
Ms. Brooke Davis
Regulatory Project Manager
USACE Wilm ington District -Asheville Regulatory Field Office
151 Patton Avenue, Room 208
Asheville, North Carolina 28801-5006
Re: Response to Reauest for Additional Information
Joint 404/401Individual Perm it Application
Duke Energy Unit 5 Inactive Ash Basin Dam Decommissioning Project, Cliffside
Steam Station
Cleveland and Rutherford Counties, North Carolina
USACE Action ID 2015-01426
Ms. Davis:
WSP USA Environm ent & Infrastructure, Inc.(WSP)and Duke Energy Carolinas, LLC(Duke Energy)
are responding herein to the US Army Corps of Engineers (USACE) request for additional
information (RAI)for the Duke Energy Unit 5 Inactive Ash Basin (U51AB) Dam Decommissioning
(DD) project located at the Cliffside Steam Station in Cleveland and Rutherford Counties, North
Carolina. Previous requestsbythe USACEforadditional information included an August 18,2023,
pre -application m eeting (first RAI) and an October 24, 2023, letter via em ail (second RAI). These
two RAls from the USACE were followed by responses from WSP, on behalf of Duke Energy, on
Septem ber 12 and Decem ber 13, 2023.
Afterthe above USACE RAlsand the respective WSP responses, conference callswere continued
with you and Mr. Sean Wallace from WSP to discuss alternative design options for the
construction of Channel 5 (outlet channel) to the Broad River, as well as other project design
components (March 6, 2024). Email correspondence was also conducted between WSP (Mr.
Wallace)and you to schedule conference call m eetingsto discussthe U51AB DD project:January
11 and March 4, 5, 18, and 20, 2024. Specifically, since the afore -mentioned December 13, 2023,
WSP RAI response correspondence, WSP engineering staff hasfurther explored the construction
of Channel 5 via two design alternatives: riprap arm oring or natural channel design. These two
Channel 5 design options, as further developed, were presented to Duke Energy for review. A
Channel 5 design (i.e.,the preferred outlet channel design —West 2 option) was selected by Duke
Energy. Other project design com ponentswere also presented by WSPto Duke Energy fortheir
review. It is noted herein that the afore -mentioned West 2 option wasfurther advanced by WSP
engineering staff to achieve the final outlet Channel 5 design, as identified throughout this RAI
response asthe West 2A design.
It isthe intent of this RAI response document to further meet the purpose and need presented
in the August 2023 Cliffside Steam Station U51AB DD Environmental Report —Joint Section
404/40 1 Individual Permit Application. The purpose is to breach and remove State Dam RUTHE-

070 (Main Dam) and, if required, State Dam RUTHE-072 (Saddle Dam) from the state dam
inventory. The project need is to address the North Carolina CAMA-14 regulatory requirements
related to ash basin closure at the U51AB DD Cliffside Steam Station and the disposal of Coal
Combustion Residual (CCR) materials in a safe and timely manner. This RAI is intended to
identify, compare, and contrast two design alternatives (i.e.,West 2A design and natural channel
design) for the construction of the outlet Channel 5 for the U51AB DD project. The RAI document
will identify and select a final design, or preferred alternative for the project action.
With the above considerations, WSP herein provides the following discussion, data, tables, and
graphic exhibits on the U51AB DD project for review by the USACE. The attached engineering
tables include:
• Table 1—Channel 5 Alternatives Sum m ary.
• Table 2 —Prelim inary Construction Cost Estim atesfor Channel 5 Alternatives.
• Table 3 —Wetlands and Stream Mitigation Cost Summary.
The attached engineering figures include Figure 1—Alternative Channel Design —West 2A (i.e.,
the Plan View drawing); Figure 2 —Alternative Channel Design Profile and Details; and Figure
3 —General Seeding Notes. The North Carolina Departm ent of Environm ental Quality (NCDEQ)
Division of Water Resources (DWR) and the North Carolina Wildlife Resources Commission
(NCWRC) have also been provided a copy of this WSP response document.
Outlet Channel 5 Design Considerations and Comparisons
WSP previously developed five concept design alternatives for outlet Channel 5 that were
presented asan attachment in the December 13,2023, WSP RAI response correspondence. The
December 12, 2023, WSP engineering Memo (U51AB DD Plan Outlet Channel Alternatives
Evaluation) discussed how each of the five alternatives differed from the original Wetlands
Impact Figure (see August 2023 Duke Energy Rogers Energy Complex —Cliffside Steam Station
Environmental Report —Joint Section 404/401Individual Permit Application, Appendix B: Plan
View and Cross -Section Drawings). Based on that m em o, Duke Energy/WSP identified the West-
2 alternative as the preferred alternative for the construction of the outlet channel to the Broad
River. Specifically, Duke Energy/WSP identified West-2 because it would result in a reduction of
USACEjurisdictional waters impacts from the originally proposed 0.9 acre for Wetland Cto 0.38
acre for this forested riparian wetland (Table 1). In March/April 2024, the West 2 design was
further developed into the West 2A design alternative which reduces the proposed impact to
Wetland Cfrom 0.38 acre to 0.29 acre (Table 1),In addition, as based on the West-2A design, the
drainage feature within the northeastern portion of Wetland C would not be impacted by the
construction of the outlet channel to the Broad River.
As discussed in the afore -mentioned December 13, 2023, RAI response, Duke Energy/WSP
considered the feasibility of natural channel design asan alternative forthe riprap-lined Channel
5. The RAI Memo discussed natural channel design feasibility and presented a conceptual
design for natural channel design principles. Duke Energy/WSP concluded that natural channel
design wasfeasible for Channel 5 considering the relatively flat channel slope with accessto the
river floodplain (see Figure NSD —1 to NSD —5 in Attachment 2—Channel 5 Natural Channel
Design in RAI December 13, 2023). However, in comparison, the natural channel design
alternative would impact a slightly larger area of Wetland C (0.40 acre) but additionally impact
the drainage feature (30 linear feet) within Wetland C (Table 1). In addition, the natural channel
design alternative wasdeterm ined to be one of the costliest alternativesforthe proposed action.
Duke Energy U51AB Dam Decommissioning Project, Cliffside Steam Station WSP
Cleveland and Rutherford Counties, North Carolina April 2024
Duke Energy Progress, LLC

For these reasons, Duke Energy and WSP excluded that natural channel design alternative
because it was not the least environmentally damaging practicable alternative (LEDPA).
The updated engineering design detailsfor the West 2A,the preferred alternative, are presented
herein, and include discussion, data, tables, and graphic exhibits. Regarding the comparison
between the West 2A preferred alternative and the natural channel design alternative, the
following additional discussion is presented to facilitate the review of the U51AB DD project
Individual Permit application bythe USACE.
Prelim inary Construction Costs Com parison
As updated herein (i.e., updates to the December 12, 2023, WSP engineering Memo), the
preliminary construction cost estimate for the West 2A preferred alternative would be $206,163
(Table 2). The estimated construction cost of the natural channel design alternative would be
higher at $329,842,which would includethe establishment ofastep/pool sequenceto the Broad
River (Table 2). Note: The estimated construction costs are for comparison purposes and do not
include construction cost items such as logistics of coordinating a specialized contractor for
natural channel construction, safety planning, mobilization, demobilization, surveying, erosion
and sediment control, access roads, and contingency. In addition, the estimated construction
costs do not include the costs of potential compensatory mitigation. Potential compensatory
mitigation costs are presented directly below.
USACE Jurisdictional Waters Impacts Comparison
West-2A, as the preferred alternative for the U51AB DD project outlet channel to the Broad River,
would impact 0.29 acre of Wetland C (forested riparian wetland). In comparison, the natural
channel design alternative would impact 0.40 acre of Wetland C and 30 linear feet of the
drainage feature within Wetland C.
The cost of compensatory mitigation for the West 2A preferred alternative would be $44,167
(Table 3). The cost of m itigation for the natural channel design alternative would be higher at
$74,865; i.e., as based on $30,460 forthe Wetland C im pact and $44,405 forthe drainage feature
im pact within the wetland (Table 3).A 2:1m itigation ratio wasapplied forthe im pact calculation
for Wetland C, a riparian forested wetland, under the West 2A preferred alternative. A 1:1
m itigation ratio wasapplied forthe im pact calculation for Wetland C underthe natural channel
design alternative.A 2:1 m itigation ratio was applied for the im pact calculation for the drainage
feature within Wetland C.
As stated in the afore-m entioned Decem ber 13, 2023, WSP RAI response correspondence to the
USACE, the North Carolina Division of Mitigation Services (NCDMS) In -Lieu Fee (ILF) Request
Form was com pleted for the proposed 0.38-acre im pact of Wetland C. The ILF Request Form
was attached to the December 13, 2023, WSP correspondence. The completed form was
submitted to Ms. Kelly Williams, In -Lieu Fee Program Coordinator, NCDMS, on December 13,
2023. The subsequent December 19, 2023, Acceptance Letter from Ms. Williams, NCDMS, was
transmitted to Ms. Lori Tollie, Duke Energy. The expiration of the Acceptance Letter is June 19,
2024. As the proposed im pact to Wetland C will be reduced from 0.38 acre to 0.29 acre under
the further advanced design for the outlet Channel 5 (i.e., the West 2A design), a new request for
com pensatory m itigation, via an updated ILF Request Form, will be subm itted by WSP to Ms.
William s, NCDMS.
Duke Energy U51AB Dam Decommissioning Project, Cliffside Steam Station WSP
Cleveland and Rutherford Counties, North Carolina April 2024
Duke Energy Progress, LLC

Extent of Riprap-lined Channelswithin Project
The total extent of new riprap-lined channels that will be constructed within the U51AB is
approxim ately 4,190 linear feet. The proposed channels within the basin following ash removal
include Channels 1,2, 3,and anew channel to be added in the southeast portion of the ash basin.
Channel 4 (see RAI December 13, 2023, Proposed Final Grades —Stage 6 Figure) is no longer
included in the design since the existing culvert isto be left in place.The extent of the proposed
riprap-lined Channel 5 (outlet channel to the Broad River), under the West 2A preferred
alternative, is approxim ately 245 linear feet or approximately 17% of the project. The majority of
the proposed riprap-lined channels in the U51AB DD project area will occur outside the Broad
River flood plain, i.e., approxim ately 4,190 linear feet for the afore-m entioned channelswith in the
basin (-- 83%). Within the floodplain area, the extent of new riprap-lined channel will only be
approximately 245 linear feet (Figure 1). Duke/WSP evaluated the cost benefit of attempting to
create a m ore natural channel design for the Channel 5 outlet; however, since the m ajority of
the U51AB project would be drained via 4,190 linear feet of riprap-lined channels, to spend
approximately double the expenses for mitigation and construction costs, the West-2A
alternative was developed to further reduce costs of the project. Duke Energy has a public
obligation to evaluate project costsfor ash basins closures because these costsare evaluated in
public rate caseswith the North Carolina UtilitiesCom mission.
Riprap Gabion-Lined Outlet
A riprap gabion-lined outlet channel is proposed at the confluence of Channel 5 and the Broad
River under the West 2A design. The point of entry into the river will not be in an upstream
alignment along the reach, but rather at a near 90-degree angle. Figure 2 presents the
Channel/Gabion Outlet Profile (i.e., Typical Gabion Outlet Section and Typical Gabion Outlet
Profile).
Selection of Preferred Design Alternative for Outlet Channel 5 Construction
Based on previous meetings, emailsand responsesfrom USACE, other agencies and the public,
the initial preferred alternative outlet channel design (August 2023)and m ost of the five concept
designs presented in the December 13, 2023 RAI, were considered ineffective except for the
natural channel design which the USACE and other agencies preferred. Therefore, Duke/WSP
continued to advance designs to develop a LEDPA. The selection of the preferred design
alternative for the construction of the outlet Channel 5 of the U51AB DD project entailed a
comparison of preliminary construction cost estimates (Table 2), constructability concerns,
permanent jurisdictional waters impacts, and compensatory mitigation costs for two principal
design alternatives: West 2A design and natural channel design. The West 2A design was
selected asthe preferred alternative over natural channel design forthe following reasons:
It isthe LEDPA:
o Least impact to Wetland C.
o No impact to Drainage Channel in Wetland C.
More cost effective:
o Construction cost estimate isthe lowest.
o Mitigation cost isthe lowest.
Constructability concerns:
o Does not require coordinating/utilizing a specialized contractor for 17% of the
channel construction of the project.
Duke Energy U51AB Dam Decommissioning Project, Cliffside Steam Station WSP
Cleveland and Rutherford Counties, North Carolina April 2024
Duke Energy Progress, LLC

o More efficiently utilizeson site m aterialsfrom project such asexisting rip -rap and
other materials vs. purchasing off site materials for natural channel design.
• Effectively meetsthe purpose and need of the project.
Other Project Considerations
Erosion Control Mattina
Erosion control matting that isfree of nylon or plastic mesh will be used as component of the
Erosion & Sedim ent Control (E&SC) Plan for revegetated areas adjacent to the disturbed portion
of Wetland C/floodplain area and where applicable, throughout the project.
Permanent Seeding of Project Area
The permanent seeding of the proposed outlet Channel 5 work area under the West 2A design
(i.e., Wetland Cdisturbed area —see Figure 1)will include the use of native grasses and fortis. Non-
native/invasive plant species wiII not be seeded within the Wetland C/floodplain disturbed areas.
Please seethe attached Figure 3 for detailson the native plant seed specifications and seeding
requirements, including the proposed plant seed specieslist.
Closing
Duke Energy/WSP appreciates your attention to this project. If you have any questions or
comments, or need additional information, please contact James Cutler at [phone] or
jam es.cutler(a)wsp.com and/or Sean Wallace at [phone] or sean.wallaceawsp.com .
Sincerely,
WSP USA Environment &Infrastructure Inc.
Jam es D. Cutler, PWS
Senior Scientist
Attachm ents: Figures 1, 2, 3 and Tables 1, 2, 3
Sean R. Wallace, PMP, PWS
Associate Scientist, Assistant Vice President
Cc: Sue Homewood (NC Division of Water Resources)
Joey Winston (NC Division of Water Resources)
Andrea Leslie (ND Wildlife Com m ision
Charlie Hiner (Duke Energy)
Michael Clough (Duke Energy)
Shahid Rahu (Duke Energy)
Mark Taylor (WSP)
Duke Energy U51AB Dam Decommissioning Project, Cliffside Steam Station WSP
Cleveland and Rutherford Counties, North Carolina April 2024
Duke Energy Progress, LLC

ROA
_ _ Q-RIVE
DRAINAGE FEATURE _�_\ _ do
/ GABION OUTLET
y
/ \ CHANNEL TOE // \
\ LIMIT OF MAY 2023 TOP O i OF SLOPE
// /(/ CHANNEL TOP / OF SLOPE
J - \CHANNEL-
-\\\\� I L\— — WEST 2A J s
— — 7///< \\ \\\ = \_ BOUNDARY OF ESTIMATED I I \ \
EARTHWORK QUANTITIES I I I \
\\ \ \ \\ ✓�\\ \\\\\ \\ \� //// /// // II // //////
// v v vii 11� v vv vvA l l 11 ll� llI III /�
i CHANNEL 1
___---
.-
-
I
12' BUFFER - -
\ o I Illlllb ESTIMATED DISTURBANCE m \ I V�\� �� WITHIN WETLAND C \ \ \ \ / / / / / / �� B
o (I \ \ 29 ACRE AREA 0
EXISTING WETLAND C \ \ \\
\ = .\ \
�( \ AREA = 0.90 ACRE
,vvw���VAvw�\v
vvv \vA
vv��vvvv
00 \ \ \\ \\\ o
vv I -- \ vvv v v ors vv v A
\cos
12' BUFFER . - \
\ \ \\\\ \ \ \\\ o \ \\ \ \ \
c
. . . - - - - - \\� \\ ��\ \
1-
-�
r) / \ \\ \
/\i
TO BE VEGETATED WITH THE
SELECTED NORTH CAROLINA
\ \� PIEDMONT RIPARIAN SEED MIX ONLY.
MAIN DAM (RUTHE-070, SCOPE 8) AND SADDLE DAM
(RUTHE-072, SCOPE 3) DECOMMISSIONING PLAN
ROGERS ENERGY COMPLEX - CLIFFSIDE STEAM STATION
WSP USA Environment &
ALTERNATIVE CHANNEL DESIGN - WEST 2A
Infrastructure Inc.
2801 YORKMONT ROAD, SUITE 100
CHARLOTTE, INC 28208 FOR F
TEL:[phone] FAX: [phone] ISSUED FOR REVIEW
LICENSSEAL URE: INC ENG: F-1253 INC GEOLOGY: C-247 SCALE: AS NOTED DES: SL
REFERENCES: DUKE
DWG TYPE: DWG DFTR: SL
1. EXISTING TOPOGRAPHIC INFORMATION WAS PRODUCED FROM PHOTOGRAMMETRIC METHODS FROM '490'ENERGY® JOB NO: 7818220026 CHKD: BG
60 60 20 FT AERIAL PHOTOGRAPHY OBTAINED ON JULY 31, 2015 BY WSP. MAIN DAM DOWNSTREAM AREA EXISTING DATE: 4/24/2024 ENGR: BG
CONDITIONS TOPOGRAPHIC SURVEY WAS DONE BY FLEMING ENGINEERING INC. (FEI) ON MAY 18, 2023.
FILENAME: APPD: MT
DWG SIZE DRAWING NO. REVISION
ANSI 11"x17" FIGURE 1 0
1 2 3 4 5 6 7 8 9 10
I I I I I I I I I
Plotted By:Lee, Seehoon Sheet Set:Cliffside Dam Decom — Alt Channel Design Layout: FIGUREI April 24, 2024 01: 26: 11 pm X:\US\USCL7500—CLT1\CAD\Duke\CliffSide\7818220026 Cliffside Closure Support\Plansheets\Dam Decommissioning Plan\Exhibit\Wetland Submittal\Altern ative Channel Design — West 2A.dwg

705
700
695
690
685
680
675
670
665
660
655
650
705
700
695
690
685
680
675
670
665
660
655
650
25+00 25+50 26+00 26+50 27+00 27+50 28+00 28+50 29+00 29+50 30+00
CHANNEL/GABION OUTLET PROFILE
HORIZONTAL SCALE: 1"=100'
VERTICAL SCALE: 1"=20'
EXISTING GRADE
3.0' 3.0'
42'
EXISTING GRADE
3:1 TIE- IN SLOPE 1.5'
3-FT. X 3-FT. X 9-FT. LONG 3.0' 3:1 TIE- IN SLOPE
1.5'
GABION BASKET
18-IN. THICK GABION MATTRESS
6-IN. NCDOT NO. 57 STONE CUSHION LAYER
8 OZ/SY NONWOVEN GEOTEXTILE
TYPICAL GABION OUTLET SECTION
PROJECTED TOP OF
GABION BASKETS
FLOW LINE OF
OUTLET DITCH
8 OZ/SY NONWOVEN GEOTEXTILE \ S :1V
18-IN. THICK GABION MATTRESS
6-IN. NCDOT NO. 57 STONE \
CUSHION LAYER \
8 OZ/SY NONWOVEN GEOTEXTILE \
TYPICAL GABION OUTLET PROFILE
1 GABION OUTLET DETAIL
N.T.S.
BROAD RIVER WATER
SURFACE AT TIME OF
CONSTRUCTION
� EXISTING GRADE
NOTE:
1. THE GABION OUTLET DETAILS ARE FROM "MAIN DAM AND SADDLE DAM
DECOMMISSIONING PLAN, INACTIVE ASH BASIN", DRAWING
CLS_C999.011.201, DATED OCTOBER 12, 2023, PREPARED BY WSP.
3H:1V �
48'
M
30'
3H:1V
2 CHANNEL WEST 2A DETAIL
jN.T.S.
"
TITLE
MAIN DAM (RUTHE-070, SCOPE 8) AND SADDLE DAM
(RUTHE-072, SCOPE 3) DECOMMISSIONING PLAN
ROGERS ENERGY COMPLEX - CLIFFSIDE STEAM STATION
ALTERNATIVE CHANNEL DESIGN PROFILE AND DETAILS
WSP USA Environment &
Infrastructure Inc.
2801 YORKMONT ROAD, SUITE 100
CHARLOTTE, NC 28208
TEL: [phone] FAX: [phone]
LICENSURE: INC ENG: F-1253 INC GEOLOGY: C-247
FOR
ISSUED FOR REVIEW
SEAL
4115DU KE
ENERGY®
SCALE: AS NOTED
DES:
SL
DWG TYPE: DWG
DFTR:
SL
JOB NO: 7818220026
CHKD:
BG
DATE: 4/17/2024
ENGR:
BG
FILENAME:
APPD:
MT
DWG SIZE
DRAWING NO.
REVISION
L11ANSIC
"x17"
FIGURE 2
0
7
I
8 9 10
I
C
0
Plotted By: Lee, Seehoon Sheet Set:Cliffside Dam Decom — Alt Channel Design Layout:FIGURE2 April 17, 2024 12:20:21pm X:\US\USCLT500—CLT1\CAD\Duke\CliffSide\7818220026 Cliffside Closure Support\Plonsheets\Dam Decommissioning Plan\Exhibit\Wetland Submittal\Alternative Channel Design — West 2A.dwg

2
7
NATIVE WETLAND SEED SPECIFICATIONS
SEEDING MIXTURE
COMMON NAME
(SPECIES)
PERCENTAGE OF MIX
Riverbank wild rye
20
(Elymus riparius)
Creeping bentgrass
15
(Agrostis stolonifera)
Fox sedge
12
(Carex vulpinoidea)
Switchgross
15
(Panicum virgatum)
Fowl bluegrass
15
(Poa palustris)
Deer tongue
$
(Dichanthelium clandestinum)
Bidens
4
(Bidens aristosa)
Soft rush
(Juncus effusus, INC Ecotype)
4
Calico aster
3
(Aster lateriflorus)
Blackeyed Susan
2
(Rudbeckia hirta)
Lanceleaf coreopsis
2
(Coreopsis lanceolata)
Total
100
NOTE: THE RECOMMENDED APPLICATION RATE FOR THE WETLAND SEED
MIXTURE ABOVE IS 20 TO 25—LBS PER ACRE. APPLY SEED MIXTURE TO
DISTURBED WETLAND, EXTENDING 10—FEET LANDWARD.
SOIL AMENDMENTS
SOIL AMENDMENTS ARE NOT TO BE APPLIED IN WETLAND AREAS
MULCH
MULCH IS NOT TO BE APPLIED IN WETLAND AREAS
MAINTENANCE
RESEED/OVER SEED IF GROWTH IS NOT FULLY ADEQUATE.
Companion Crops
Species
Common
Season
Mix
Notes:
Secale
Cereal or Winter
Early Spring or Fall
30 Ibs/acre
Grows 3-4' tall, but not a strong
cereale
rye
competitor.
Lolium
Perennial rye
Early Fall or Spring
20-50%
Shorter rye; lasts about 2 years, then
perenne
dies out.
Urocloa
grown Top Millet
Spring, Summer
20-50%
Good germination; dies off with
ramose
frost; does not tolerate mowing.
To provide
quicker establishment of groundcover, the Riparian Seed Mix specified above should
also be augmented with the appropriate cover/companion species in this table.
1 GENERAL SEEDING NOTES WETLAND AREAS
NITS
GENERAL SEEDING REQUIREMENTS FOR WETLAND AREAS
DEFINITION
CONTROLLING RUNOFF AND EROSION ON DISTURBED WETLAND AREAS BY
ESTABLISHING PERENNIAL VEGETATIVE COVER WITH NATIVE WETLAND SEED.
TO REDUCE EROSION AND DECREASE SEDIMENT YIELD FROM DISTURBED AREAS, AND
TO PERMANENTLY STABILIZE SUCH AREAS IN A MANNER THAT IS ECONOMICAL, ADAPTS
TO SITE CONDITIONS, AND ALLOWS SELECTION OF THE MOST APPROPRIATE PLANT
MATERIALS
SEEDBED REQUIREMENTS
TO MAINTAIN A GOOD STAND OF WETLAND VEGETATION, THE SOIL MUST BE WETLAND
SOIL REMOVED FROM NEARBY DISTURBED AREAS AND STOCKPILED OR IMPORTED
WEED -FREE TOPSOIL APPROVED BY THE ENGINEER. REUSED WETLAND SOIL AND TOP
SOIL SHOULD ALSO HAVE THESE CRITERIA:
• FREE FROM LARGE ROOTS, BRANCHES, STONES, LARGE CLODS OF EARTH, OR
TRASH OF ANY KIND.
SEEDBED PREPARATION
INSTALL NECESSARY ADJACENT (NOT IN WETLAND) MECHANICAL EROSION AND
SEDIMENTATION CONTROL PRACTICES BEFORE SEEDING, AND RETURN GRADES TO
ORIGINAL CONTOURS AS MUCH AS PRACTICABLE.
ROUGHEN WETLAND SURFACES BY DISKING, RAKING, HARROWING, OR OTHER SUITABLE
METHODS PRIOR TO SEEDING.
BROADCAST SEED INTO A FRESHLY LOOSENED SEEDBED THAT HAS NOT BEEN SEALED
BY RAINFALL.
SEEDING
USE CERTIFIED SEED ONLY FOR NATIVE WETLAND SEEDING.
LABELING OF NON -CERTIFIED SEED IS ALSO REQUIRED BY LAW. LABELS CONTAIN
IMPORTANT INFORMATION ON SEED PURITY, GERMINATION, AND PRESENCE OF WOOD
SEEDS. SEEDS MUST MEET STATE STANDARDS FOR CONTENT OF NOXIOUS WEEDS. DO
NO ACCEPT SEED CONTAINING "PROHIBITED" NOXIOUS WEED SEED.
APPLY SEED UNIFORMLY BY HAND OR WITH A PORTABLE BROADCAST SPREADER
WHEN USING BROADCAST -SEEDING METHODS, SUBDIVIDE THE AREA INTO WORKABLE
SECTIONS AND DETERMINE THE AMOUNT OF SEED NEEDED FOR EACH SECTION. APPLY
ONE-HALF THE SEED WHILE MOVING BACK AND FORTH ACROSS THE AREA, MAKING A
UNIFORM PATTERN: THEN APPLY THE SECOND HALF IN THE SAME WAY, BUT MOVING AT
RIGHT ANGLES TO THE FIRST PASS.
DO NOT APPLY MULCH IN WETLANDS. DO NOT APPLY FERTILIZER.
NAA IAI-1 A
INSPECT SEEDED AREAS FOR LARGE-SCALE FAILURE AND MAKE NECESSARY REPAIRS
AND RESEEDINGS WITHIN THE SAME SEASON, IF POSSIBLE.
IF A STAND HAS INADEQUATE COVER, RE-EVALUATE CHOICE OF PLANT MATERIALS.
RE-ESTABLISH THE STAND AFTER SEEDBED PREPARATION OR OVERSEED THE STAND.
SEEDING SPECIFICATIONS
SEE TABLE FOR WETLAND SEEDING AND RIPARIAN SPECIFICATIONS. FESCUE AND
SERICEA LESPEDEZA ARE PROHIBITED IN WETLAND AREAS.
NN%I)
WSP USA Environment &
Infrastructure Inc.
2801 YORKMONT ROAD, SUITE 100
CHARLOTTE, NC 28208
TEL:[phone] FAX: [phone]
LICENSURE: NC ENG: F-1253 NC GEOLOGY: C-247
SEAL
TITLE
MAIN DAM (RUTHE-070, SCOPE 8) AND SADDLE DAM
(RUTHE-072, SCOPE 3) DECOMMISSIONING PLAN
ROGERS ENERGY COMPLEX - CLIFFSIDE STEAM STATION
GENERAL SEEDING NOTES
FOR
ISSUED FOR REVIEW
40)DUKE
E N E nt"'
SCALE: AS NOTED
DES:
SL
DWG TYPE: DWG
DFTR:
SL
JOB NO: 7818220026
CHKD:
BG
DATE: 4/17/2024
ENGR:
BG
FILENAME:
APPD:
MT
DWG SIZE
DRAWING NO.
FIGURE 3
REVISION
ANSI
11"x17"
0
8 9 10
C
-n
^
U J
C
m
W
0
Plotted By Lee, Seehoon Sheet Set Chffsde Dom Decom — Alt Channel Design Layout -FIGURES April 17, 2024 05. 33-04pm X_\US\USCLT500—CLT1\CAD\Duke\CliffSide\7818220C26 Cliffside Closure Support\Plo heets\Dam Decommissioning Plan\Exhibit\Welland Submittal\Alternative Channel Design — West 2A_dwg

USIAB DDP Outlet Channel Design Alternatives Evaluation
Rogers Energy Complex, Cliffside Steam Station
Rutherford County, North Carolina
Revision 2, 4/17/2024
filnrSQi:ST.T.T]W
Channel 5 Alternative
Channel
Bottom
Top
Length
Longitudinal
Channel
Channel
Estimated
Estimated
Estimated
Cut
Fill
Channel Description
Pros
Cons
Depth (ft)
Width
Width
(ft)
Slope
Capacity
Lining
Wetlands
Wetlands
Drainage Feature
(CY)
(CY)
(ft)
(ft)
(ft/ft)
(cfs)
Disturbance
Disturbance
(Stream)
(ac)
(%)
Disturbance (ft)
DDP Design Rev 1
Minor grading in the U51AB exit area.
Largest area of wetlands disturbance
Current Design
Central location divides thewetlands leaving
(WSP Memo (12/13/23) -
z
30
az
211.0
0.0107
416s
Class B
o.90
100.0%
142
o
z,1ao
small/isolated areas
Figure 1)
Riprap
p p
Potentially challenging subgrade conditions for
construction.
DDP Design Rev 1
Minor grading in the IAB exit area
Slightly less area of wetlands disturbance
Alternative
alignment - reduced
Less fill required in comparison to design channel
Central location divides the wetlands leaving
Channel 5
Class B
bottom width/
Reduces wetlands disturbance compared to design
small/isolated areas
(WSP Memo (12/13/23) -
3
12
30
211.0
0.0307
420.4
Riprap
0.64
71.3%
142
0
1,850
increased depth.
p
channel
Potentially challenging sub rade conditions for
Y Bi B B
Attachment 1)
construction
Channel starts from
Lower estimated wetlands disturbance compared to
Tree clearing and excavation west of the design
West 1
Class
Channel 5 high paint,
design channel; under 0.5 acre
channel
(WSP Memo (12/13/23) -
3
16
34
286.0
0.0070
418.9
0.47
52.4%
0
2,088
775
alignment moved west.
Conveys flow to existing U51AB primary/auxiliary
Requires re -grading U51AB Channel 1 to Channel
Attachment 1)
Riprap
outlet channel to the river
West-1 transition with a down chute
Channel West -1 alignment
Lower estimated wetlands disturbance of the
Increased tree clearing and excavation area to the
upper areas moved further
alternatives
west ofthe proposed channel
West
west to avoid wetlands.
Conveys flow to existing U51AB primary/auxiliary
Channel 1 to Channel West-2 transition will require
(WSP Memo (12/13/23) -
3
16
34
380.0
0.0079
445.0
Class B
Riprap
o.38
42.3%
D
1,954
1,179
outlet channel to the river
down chute
USIAB final grades need to be revised at the U51AB
Attachment 1)
exit area
Channel alignment moved
Lowest estimated wetlands disturbance of the
Increased tree clearing and excavation area to the
further west to avoid
alternatives
west ofthe proposed channel
West 2a
wetlands. U pperstrea no
USIAB final grades need to be revised at the U51AB
(Figure 1)
3
30
48
245.0
0.0070
700.7
Class B
Riprap
0.29
32.3%
0
2,722
507
channel alignments
modified per the exit
exit area (work in Progress)
(Notes 4 and 5 )
channel (West 2a).
Channel 5 alignment
Shift wetlands impacts to the east and does not
Major excavation area to the east ofthe channel in
moved further east to avoid
divide the wetlands
the vicinity ofthe transmission tower
East
wetlands.
Insignificant reduction in wetlands disturbance
(WSP Memo (12/13/23) -
3
12
30
341.0
0.0117
440.0
Class B
0.59
65.7%
142
3,000
1,834
Potentially challenging subgrade conditions for
Attachment 1)
Riprap
onstruction
Natural Channel Design:
Natural stream design likely replicates conditions
Insignificant reduction in wetlands disturbance
combination of cross vanes,
before the dam and U51AB was constructed
Potentially challenging subgrade conditions for
Natural Channel Design
Boulder,
Rockand
step pools, and riffles
construction
((WSP Memo (12/13/23)-
N/A
N/A
N/A
319.0
0.03 to 0.06
N/A
Rock,
0.40
44.6%
30
1,300
gravel -
Attachment 2)
Riffles, Step
Pools
unknown
quantity
1. Existing Wetlands C Area = 0.9 ac
2. Permit design flow rate for USIAB exit channel= 416 cfs. Channel side slopes are 3H:1V.
3. The wetlands disturbance acreages reported above are estimated based on preliminary grading. Actual acreages may change when the selected channels are graded with Main Dam footprint modification.
4. The U51AB final grades and U51AB channels are currently being revised based on actual U51AB bottom of ash grades. Based on this update, Channel West 2a geometry may be revised. If West 2a geomery is revised, the reported total wetlands disturbance (0.29 acres) will not be exceeded.
5. To be comparable to the other alternative channel options, the reported earthwork quantities do not include the gabion outlet area.

U51AB DDP Outlet Channel Design Alternatives Evaluation
Rogers Energy Complex, Cliffside Steam Station
Rutherford County, North Carolina
Revision 2, 4/17/2024
Table 2. Preliminary Construction Cost Estimates for Channel 5 Alternatives
CHANNEL ID
ITEM NO.
DESCRIPTION
ENGINEER'S
ESTIMATED
QUANTITIY
UNITS
ESTIMATED
UNIT PRICE
ESTIMATED PRICE
COMMENTS
1-1
Clearing and Grubbing
0.90
AC
$13,000
$11,671
Wetlands C disturbed area
1-2
Cut from Western/Eastern Slopes)
0
CY
$5.0
$0
See Table 1, earthworks based on AutoCAD volume anal se
Current Design
1-3
1-4
Fill (for Channel Construction)
Rip,. -Channel
2,180
528
CY
CY
$5.0
$102.0
$10,900
$53,805
See Table 1, earthworks based on AutoCAD volume analyses
=(Top Width+3ft'Ch. Len h"1.5 ft'(1/27), [rip,.p thlcknes-1.5ft
(WSP Memo
1-5
8 oz/sy Geotextile-Channel
1,055
5Y
$2.5
$2,638
=(Top Width+3 ft)'Ch. Len th'(1/9)
(12/13/23)-
1)
1-6
Erosion Control Matting -Cut Slo es
4,900
SF
$3.5
$17,150
Channel side slope area
Figure
1-7
Temporary Seeding -Cut/Fill Slopes
0.11
AC
$3,000
$337
Channel side slope area
1-8
Permanent Seeding-Cut/Fill Slopes
0.11
AC
$4,000
$450
Channel side slope area
1-9
Total Miti ation Cost
1
IS
$346,913
$346,913
See Table 3
Channel 5- Current
Design Total
$443,864
2-1
Clearing and Grubbing
0.64
AC
$13,000
$8,320
Wetlands C disturbed area
2-2
Cut from Western/Eastern Slopes)
0
CY
$5.0
$0
See Table 1, earthworks calculated based on length x width x depth
Alternative
2-3
Fill (for Channel Construction)
1,850
CY
$5.0
$9,250
See Table 1, earthworks calculated based on length x width x depth
Channel
2-4
Ri ra -Channel
387
CY
$102.0
$39,457
=(Top Width+aft"Ch. Len h"1.5 ft'(1/27), [,ip,.p thickness=1.5 ftl
(WSP Memo
2-5
8 oz/sy Geotextile - Channel
774
5Y
$2.5
$1,934
=(Top Width+3 ft)'Ch. Length'(1/9)
(12/13/23) -
2-6
Erosion Control Matting -Cut/Fill Slopes
4,900
SF
$3.5
$17,150
Assume same as Item No. 1-6
Attachment 1)
2-7
Temporary Seeding -Cut/Fill Slopes
0.11
AC
$3,000
$337
Assume same as Item No. 1-7
2-8
Permanent Seeding -Cut/Fill Slopes
0.11
AC
$346,913
$39,024
Assume same as Item No. 1-8
2-9
Total Mitigation Cost
1
IS
$307,658
$307,658
See Table 3
Alternative
Channel S Total
$423,130
3-1
Clearing and Grubbing
0.74
AC
$13,000
$9,584
Wetlands C disturbed area+ Disturbed area outside Wetland
3-2
Cut (from Western/Eastern Slopes)
2,088
CY
$5.0
$10,440
See Table 1, earthworks based on AutoCAD volume analyses
1
3-3
Fill for Channel Construction
775
CY
$5.0
$3,875
See Table 1, earthworks based on AutoCAD volume analyses
West
3-4
Ripra -Channel
588
CY
$102.0
$59,965
1 =(Top Width+3 ft)'Ch. Len h'1.5ft'(1/27),[riprap thickness=1.5 ftl
(WSP Memo
3-5
8 oz/sy Geotextile- Channel
1,176
SY
$2.5
$2,939
=To Wid[h+3ft"Ch. Lenth'1/9
(12/13/23)-
Attachment 1)
3-6
Erosion Control Matting -Cut/Fill Slopes
9,682
SF
$3.5
$33,887
Total cut/fill areas from Figure 3
3-7
Tem o Seeding -Cut/Fill Slopes
0.22
AC
$3,000
$667
Total cut/fill areas from Figure 3
3-8
Permanent Seeding -Cut/Fill Slopes
0.22
AC
$346,913
$77,108
Total cut/fill areas from Figure 3
3-9
Total Mitigation Cost
1
LS
$71,581
$71,581
See Table 3
Alternative Channel
- West 1Total
$270,046
4-1
Clearing and Grubbing
0.64
AC
$13,000
$8,343
Wetlands C disturbed area+ Disturbed area outside Wetland
4-2
Cut from Western/Eastern Slopes)
1,954
CY
$5.0
$9,770
See Table 1, earthworks based on AutoCAD volume anal se
West
4-3
Fil I(for Chan nel Construction)
1,179
CY
$5.0
$5,895
See Table 1,earthworks based on AutoCAD volume a n alyses
4-4
Ri ra -Channel
781
CY
$102.0
$79,673
=(Top Width+3ft'Ch. Len h"1.5 ft'1/27, [riprap thickness 1.5ft
(WSP Memo
4-5
8oz/sy Geotextile- Channel
1,562
5Y
$2.5
$3,906
=(Top Width+3 ft)'Ch. Len th'(1/9)
(12/13/23)-
1)
4-6
Erasion Control Matting - Cut/Fill Slopes
10,644
SF
$3.5
$37,254
Total cut/fill areas from Figure 4
Attachment
4-7
Temporary Seeding - Cut/Fill Slopes
0.24
AC
$3,000
$733
Total cut/fill areas from Figure
4-8
Permanent Seeding -Cut/Fill Slopes
0.24
AC
$346,913
$84,769
Total cut/fill areas from Figure 4
4-9
Total Mitigation Cost
1
IS
$57,874
$57,874
See Table 3
Alternative Channel
- West 2Total
$288,217
4a-1
Clearing and Grubbing
0.58
AC
$13,000
$7,540
Wetlands C disturbed area+ Disturbed area outside Wetland
4a-2
Cut (from Western/Eastern Slopes)
2,722
CY
$5.0
$13,610
See Table 1, earthworks based on AutoCAD volume analyses
4a-3
Fill for Channel Construction
507
CY
$5.0
$2,535
See Table 1, earthworks based on AutoCAD volume analyses
West 2a
4a-4
Ri ra -Channel
694
CY
$102.0
$70,805
=(Top Width+3 ft)'Ch. Length - 1.5 ft'(1/27),[ri rap thickness=l.5 ftl
(Figure l)
4a-5
8 oz/sy Geotextile - Channel
1,388
SY
$2.5
$3,471
=(Top Width+3ft'Ch. Lenth"1/9
(Note 4)
4a-6
Erosion Control Matting -Cut/Fill Slopes
9,382
SF
$3.5
$32,837
Total cut/fill areas from Figure 1
4a-7
TemporaryTemponary Seeding -Cut/Fill Slopes
0.22
AC
$3,000
$646
Total cut/fill areas from Figure I
4a-8
Permanent Seeding - Cut/Fill Slopes
0.22
AC
$346,913
$74,719
Total cut/fill areas from Figure 1
4a-9
Total Mitigation Cost
1
LS
$44,167
$44,167
See Table 3
Alternative Channel
- West 2a Total
$250,330
5-1
Clearing and Grubbing
0.95
AC
$13,000
$12,312
Wetlands C disturbed area + Disturbed area outside Wetland C
5-2
Cut from Western/Eastern Slo es
3,000
CY
$5.0
$15,000
See Table 1, earthworks based on AutoCAD volume anal ses
East
5-3
Fill (for Channel Construction)
1,834
CY
$5.0
$9,170
See Table 1, earthworks based on AutoCAD volume analyses
5-4
Ri ra -Channel
625
CY
$102.0
$63,767
=(Top Width+3ft'Ch. Len h"1.5 ft'1/27, [rip,. thlcknes-1.5ft
(WSP Memo
5-5
8oz/sy Geotextile- Channel
1,250
5Y
$2.5
$3,126
=(Top Width+3 ft)'Ch. Lcngth'(1/9)
(12/13/23)-
1)
5-6
Erosion Control Matting -Cut/Fill Slopes
22,262
SF
$3.5
$77,917
Total cut/fill areas from Figure 5
Attachment
5-7
Temporary Seeding -Cut/Fill Slopes
0.51
AC
$3,000
$1,533
Total cut/fill areas from Figure
5-8
Permanent Seeding -Cut/Fill Slopes
0.51
AC
$346,913
$177,295
Total cut/fill areas from Figure 5
5-9
Total Mitigation Cost
1
IS
$300,043
$300,043
See Table 3
Alternative Channel
- East l Total
$660,163
Natural Channel
5-1
n and Grubbin
Clearin!
0.76
AC
$13,000
$9,842
Wetlands C disturbed area+ Disturbed area outside Wetland
Design
5-2
Natural Channel Construction
1
IS
$320,000.0
$320,000
Cost based on 1/26/2024 KBS Earthworks CourtesyQuote
((WSP Memo
5-3
Total Mitigation Cost
1 1
1 LS
$74,865
$74,865
See Table 3
Alternative Channel-
Natural Channel
Design Total
$404,707
1. This preliminary cost estimate is prepared for comparison of the proposed alternatives and does not include construction cost items such as safety planning, mobilization, demobilization, surveying, erosion and sediment control, access roads, and
contingency.
2. Unit price estimates are based on Sequoia's December 6, 2023 dated email to WSP.
3. Riprap unit cost: $85/ton from Sequoia. Assume 1.2 tons/CY and $102/Cy.
4. To be comparable to the other alternative channel options, the reported earthwork quantities do not include the gabion outlet area.

U51AB DDP Outlet Channel Design Alternatives Evaluation
Rogers Energy Complex, Cliffside Steam Station
Rutherford County, North Carolina
Revision 2, 4/17/2024
Table 3. Wetlands and Stream Mitigation Cost Summary
Wetland C Impact
Wetland Mitigation
Wetland Mitigation
New Drainage
Stream Mitigation
Stream
Channel 5 Design Alternative
Feature Impact
Total Mitigation Cost
(acre)
Ratio X:1
Cost
Ratio X:1
Mitigation Cost
(linear feet)
Current Design
(WSP Memo (12/13/23) -
0.90
2
$136,728
142
2
$210,186
$346,913
Figure 1)
Alternative
Channe15
0.64
2
$97,472
142
2
$210,186
$307,658
(WSP Memo (12/13/23) -
t1
West 1
(WSP Memo (12/13/23) -
0.47
2
$71,581
0
2
$0
$71,581
Attachment 1)
West 2
(WSP Memo (12/13/23) -
0.38
2
$57,874
0
2
$0
$57,874
Attachment 1)
West 2a
(Figure 1)
0.29
2
$44,167
0
2
$0
$44,167
(Note 5)
East
(WSP Memo (12/13/23) -
0.59
2
$89,857
142
2
$210,186
$300,043
Attachment 1)
Natural Channel Design
((WSP Memo (12/13/23) -
0.40
1
$30,460
30
2
$44,405
$74,865
Attachment 2)
1. Potential mitigation costs based on NC Division of Mitigation Services (NCDMS) In -Lieu Fee Program rates for Standard Service Areas. Current NCDMS rates are effective through June 30, 2024.
2. Wetland cost per credit = $76,150.13; Stream cost per credit = $740.09.
3. Natural Channel Design Wetland C Impact estimated to be 0.32 acres. Rounded up to 0.40 acres for contingency.
4. Natural Channel Design New Drainage Feature Impact estimated to be 26 ft. Rounded up to 30 ft for contingency.
5. If West 2a geomery is revised, the reported total wetlands disturbance (0.29 acres) will not be exceeded.