20170149 Ver 2 _USACE PN RAI Response - IP signed pkg _20180910

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Mr. Bryan Roden -Reynolds September 10, 2018
Charlotte Regulatory Field Office
U.S. Army Corps of Engineers
151 Patton Avenue, Room 208
Asheville, North Carolina 28801-5006
RE: Response to Reauest for Additional Information
USACE Action ID: SAW -2015-01412
Marshall Steam Station Stormwater Redirection Project Individual Permit
Application
Sherrills Ford, Catawba County, North Carolina
Dear Mr. Roden -Reynolds:
Duke Energy Carolinas, LLC (Duke Energy), in consultation with Wood Environment &
Infrastructure Solutions, Inc. (Wood) (formerly Amec Foster Wheeler), submitted a
standard permit application on June 29, 2018 to the Charlotte Regulatory Field Office of
the U.S. Army Corps of Engineers (USACE) for issuance of Section 404 Individual
Permit (IP) for the Marshall Steam Station Stormwater Redirection Project at the
Marshall Plant in Sherrills Ford, Catawba County. Subsequent to the review of the
application and supporting documents as provided in the Public Notice (advertised on
June 29, 2018), responses were given by four federal and state agencies. The four
agencies that provided responses to the Public Notice included: North Carolina
Department of Environmental Quality, Division of Water Resources (NCDEQ-DWR);
North Carolina Wildlife Resources Commission (NCWRC); North Carolina Department of
Natural and Cultural Resources, State Historic Preservation Office (NC-SHPO); and
National Oceanic and Atmospheric Administration, National Marine Fisheries Service
(NMFS). Wood received the set of agency responses on August 10, 2018 via email
correspondence from you to Mr. Steve Cahoon, Duke Energy. Responses to the
NCWRC comments are presented below. Responses to the comments provided by you
in the August 10, 2018 USACE email correspondence to Mr. Cahoon are also provided
below. The NMFS, in correspondence to the USACE dated July 5, 2018, stated that the
proposed project would not occur within the vicinity of essential fish habitat. The NC-
SHPO, in correspondence to the USACE dated July 19, 2018, stated that the agency
had no comments on the proposed project. As such, the set of responses to requests for
additional information herein does not include discussion regarding the NMFS or the NC-
SHPO. Finally, the NCDEQ-DWR, in email correspondence to the USACE dated July
20, 2018, stated that the agency "will not be submitting any comments through the
Public Notice process". Any comments regarding the proposed project that are provided
by the NCDEQ-DWR outside of the Public Notice process will be addressed by the
permittee under separate correspondence to the NCDEQ-DWR. A copy of those
responses to NCDEQ-DWR comments will be provided to the USACE.

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USACE
C;nmmPnt 1
With regards to the recommendation made by NCWRC related to the avoidance of tree
clearing during the maternity roosting season from May 1511 through August 15th to
reduce the probability for take of the Northern Long-eared Bat (Myotis septentrionalis);
the Corps highly recommendations the applicant consult with the U.S. Fish and Wildlife
Service (Mr. Byron Hamstead, USFWS, Asheville Field Office) to determine potential
impacts to the Northern Long-eared Bat from the proposed project.
Response
No Northern Long-eared Bat hibernacula or known maternity roost trees occur at or
within 0.25 mile of the Project area based on the results of the February 22, 2018 North
Carolina Natural Heritage Program (NCNHP) database inquiry requested by Wood. Tree
removal activities that are not within 0.25 mile (0.4 kilometer) of a known hibernaculum
would not constitute incidental take of the species (50 CFR § 17.40(0)). In addition, tree
removal in general does not constitute incidental take unless a tree is a known maternity
roost tree and the removal is performed during the pup season (identified as June 1 to
July 31 in the 4(d) rule). However, Duke Energy understands the NRWRC
recommendation to implement a cutting moratorium during project construction from
May 151h through August 15th to reduce the probability for take of the species. Therefore,
under the recommendation from the USACE to initiate consultation with the USFWS,
Wood contacted Mr. Byron Hamstead on August 27, 2018, USFWS Asheville Ecological
Services Field Office, for consultation on this matter; specifically, the implementation of a
cutting moratorium (May 15th through August 15th) during project construction as related
to the potential effect on the species by the proposed action. The following salient points
were discussed and confirmed:
• The Endangered Species Act 4(d) Rule would apply for the Stormwater
Redirection project at the Marshall Steam Station.
• No Northern Long-eared Bat known maternity roost trees or known hibernacula
occur in Catawba County based on available data.
• The tree clearing `moratorium' (during the maternity roosting season) from May
15th through August 15th. would be a voluntary measure by the permit applicant
for the Stormwater Redirection project; i.e., it would not be a mandatory action
required by regulatory agencies, specific to the Stormwater Redirection project at
the Marshall Steam Station.
• The USFWS recommends that, if tree clearing is to be conducted at the project
site during the May 15th through August 15th timeframe, that the clearing be
conducted at the front end of this timeframe.
Comment 2
The analysis of the project purpose is a critical first step in the Corps permitting process.
The Corps is responsible in all cases for independently defining the project purposes
from both the applicant's and the public's perspective. Initially, the Corps evaluates a
project's "basic purpose" to assess whether the project is water dependent. Once the
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Corps has determined the water dependency of the project, it no longer considers the
basic project purpose, but analyzes practicable alternatives in the light of the "overall
project purpose". The overall project purpose must be specific enough to define the
applicant's need, but not so restrictive as to preclude an analysis of all reasonable
alternatives. The project purpose stated in your application is "to redirect stormwater to
ensure the long-term integrity of Coal Combustion Residual (CCR) materials and
facilitate future ash basin closure activities within Marshall Steam Station." In considering
the overall project purpose, we have determined that this project purpose does not
capture the project function in its entirety and does not provide reason (i.e., addressing
the North Carolina regulatory requirements for phasing out wet ash handling) for the
construction/operation of this project. Therefore, we have determined the overall project
purpose of this project is to redirect stormwater and jurisdictional Waters of the United
States, to ensure the long-term integrity of CCR materials and to facilitate future ash
basin closure activities within Marshall Steam Station that comply with the North
Carolina Coal Ash Management Act of 2014.
Response
Duke Energy concurs with the interpretation of the overall project purpose of the
Marshall Steam Station Stormwater Redirection Project as now defined by the USACE.
As now defined, the overall project purpose of the project is "to redirect stormwater and
jurisdictional Waters of the United States, to ensure the long-term integrity of CCR
materials and to facilitate future ash basin closure activities within Marshall Steam
Station that comply with the North Carolina Coal Ash Management Act of 2014."
Comment 3
In Section 4.3.2 (Pump Alternative) you state the following, "The Pump Alternative would
require extremely large and oversized pumps since it would be impractical to pond and
attenuate flows. The activity would require significant capital costs, as well as operation
and maintenance (O&M) costs. To handle the flows, all piping would need to be large
and oversized. The risk of pump failure and the pumping in perpetuity are drawbacks to
this alternative." These are general statements for the applicant's reasons not to pursue
the Pump Alternative; however, they are not specific or detailed enough for the Corps to
analyze. Therefore, please provide additional information/specific details for the following
areas of concern related to the Pump Alternative: a) size/dimension, horsepower,
capacity, etc. of pumps; b) capital costs of Pump Alternative versus capital costs of
chosen alternative (i.e. Gravity and Pumped Alternative); c) O&M costs of Pump
Alternative versus O&M costs of chosen alternative (i.e., Gravity and Pumped
Alternative); d) pipe sizing, material, length of pipe, etc. to be used in the Pump
Alternative; and e) risk of pump failure for an oversized pump compared to the pump
failure for the pump selected in the chosen alternative.
Response
There are four distinct drainage areas that require management to bypass stormwater
that is currently managed by the four culverts that pass beneath the Structural Fill. There
are currently jurisdictional areas (streams and wetlands) associated with three of these
four culverts. In order to route the stormwater around the Structural Fill and prevent

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impact to these jurisdictional areas, stormwater cannot be allowed to be impounded at
the stormwater management sites and stormwater will have to be conveyed by pumping.
Topographical and property constraints indicate that the only feasible alternative to
manage stormwater while not impacting jurisdictional areas is to construct a pump
station at each of the four stormwater features and convey the stormwater to an existing
creek located along the south side of the Marshall Steam Station. See figure below for
general layout.
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While pumping of stormwater in perpetuity is generally considered impractical from an
engineering and economic perspective when a gravity alternative is available, it is
technically feasible to manage the stormwater redirection by pumping. Any pumping
system will be designed to prevent impounding of stormwater within adjacent
jurisdictional areas and will need to operate as needed forever. Project criteria has
established the 25- year — 24-hour design storm (6 -inches) as the largest event that will

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be managed by the pump stations. With external storage not available (to prevent
impacts to jurisdictional areas), stormwater can be stored only within the wetwells
associated with each pump station and must be pumped as the levels within any of the
pump stations reach action levels. Two to four pumps will be located within each pump
station to provide service through the anticipated range of inflow rates and to provide
contingency against individual pump failure.
Backup diesel powered generators would be required for each pump station to mitigate
electrical power interruptions or failure that could result in the ponding of stormwater
within jurisdictional areas. The diesel emissions and fuel storage will have a net negative
impact on the environment compared with management of stormwater by gravity.
Gravity solutions are more reliable and require less maintenance.
For the selected design storm, each pump station would be designed to manage the
following flows:
The total pumping capacity within each pump station will be managed by two to four
pumps instrumented to alternate starts to minimize wear.
The forcemain would extend from the pump stations south along Duke Energy property
to the north and west of the closed FGD Landfill, and ultimately discharge into
Beaverdam Creek. The total estimated total length of this buried forcemain is 6,000 feet
(1.1 miles).
Detailed design of the pump stations and forcemain has not been conducted, but
engineering criteria have been established to further define this alternative. Assumed
criteria are provided below:
• Project duration: 100 -years (for estimating purposes only - pumping is continuous)
• Site improvements: Paved access road, fencing, grading
• Wetwells: Subsurface reinforced concrete
• Pumps: Minimum two pumps per pump station. Service range = 3,500 gpm to
18,000 gpm (10 hp to 80 hp)
• Backup diesel generators at each pump station (air permits required)
• 24 -inch HDPE forcemain
• Service life (replacement):
• Wetwells = 35 years (2 replacements per 100 years)
• Pumps = 15 years (5 replacements per 100 years per pump)
G9
DRAINAGE
FLOW
TOTAL PUMP
PUMP
AREA
CAPACITY
STATION
(ACRES)
(MGD) (25
(GPM) (25 yr)
r
#1 (At Pipe #1)
16
15
10,500
#2 At Pipe #2
65
35
24,400
#3 At Pipe #3
38
30
20,900
#4 At Pipe #4
56
75
52,100
The total pumping capacity within each pump station will be managed by two to four
pumps instrumented to alternate starts to minimize wear.
The forcemain would extend from the pump stations south along Duke Energy property
to the north and west of the closed FGD Landfill, and ultimately discharge into
Beaverdam Creek. The total estimated total length of this buried forcemain is 6,000 feet
(1.1 miles).
Detailed design of the pump stations and forcemain has not been conducted, but
engineering criteria have been established to further define this alternative. Assumed
criteria are provided below:
• Project duration: 100 -years (for estimating purposes only - pumping is continuous)
• Site improvements: Paved access road, fencing, grading
• Wetwells: Subsurface reinforced concrete
• Pumps: Minimum two pumps per pump station. Service range = 3,500 gpm to
18,000 gpm (10 hp to 80 hp)
• Backup diesel generators at each pump station (air permits required)
• 24 -inch HDPE forcemain
• Service life (replacement):
• Wetwells = 35 years (2 replacements per 100 years)
• Pumps = 15 years (5 replacements per 100 years per pump)
G9

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• Generators = 15 years (4 replacements per 100 years per generator)
• Forcemain = 50 years (1 replacement per 100 years)
• Annual O&M by Duke Energy staff and maintenance agreement = 100 years
A summary of the estimated costs (2018 dollars) to construct, operate and replace the
stormwater redirecting systems over 100 -years is shown below.
100 YEAR LIFE CYCLE COSTS FOR PUMPING AND CONVEYANCE
Line Item
Description
Unit
Quantity
Unit Price
Amount
Site Work Including Grading for
1
Pumpstation, Pump Station Fencing, Asphalt
LS
4
$ 691,619
$ 2,766,478
for Pump Station, and Valve Vaults in
Station Yard
2
Grouting Existing Culverts
LS
4
$ 775,000
$ 3,100,000
3
Asphalt Access Road
LS
1
$ 1,237,616
$ 1.237,616
4
Pumps wl Control Panel, Station Piping,
LS
4
$ 724,663
$ 2,898,652
Equipment Vaults, and Wet Well
5
24" HDPE Forcemain wlExcavation and
LS
1
$ 2,307,752
$ 2,307,752
Bores
6
Electrical- VFDs, Generator, SCADA, ATS,
LS
4
$ 657,616
$ 2,630,462
MTS, Building Electrical, & Lighting
7
Pump, Generator, & ATS Replacement Over
LS
20
$ 280,553
$ 5,611,069
100 Years (5 Replacements per Station)
8
Annual O&M
Years
100
$ 249,525
$ 24,952,455
Total Pump Station Replacements
9
(Assuming 33 Year Life Cycle Cost for
EA
8
$ 3,642,404
$ 29,139,232
Each Station) Includes Line Items 1 2 4 &
10
Forcemain Replacement (Assuming 50 Year
EA
1
$ 2,307752
$ 2,307,752
Life Cycle Cost)
Subtotal ................ .................... $ 76,951,469
Contingency (20%) ................ .................... $ 15,390,294
'Total ................................... $ 92,341,800
'All casts in 2018 dollars- Construction costs will likely increase over time due to inflation
Until the final cover is in place over the Ash Basin, the Swale will discharge into two
Temporary Stormwater Ponds. As a first step, the CCR material with the portion of the
Ash Basin used for stormwater management will be removed and backfilled with
controlled compacted fill to construct the Temporary Stormwater Ponds. The Temporary
Stormwater Ponds (West Temporary Stormwater Pond and East Temporary Stormwater
Pond) will be lined with a 40 -mil LLDPE liner, and selected areas will be covered with a
4 -inch uniform section grout filled fabric formed revetment for ballast and for operations
and maintenance and potential cleanout of the ponds. The Temporary Stormwater
Ponds will be constructed in two phases with the West Temporary Stormwater Pond
being constructed first, followed closely by the East Temporary Stormwater Pond. The
two stormwater ponds will be connected to each other by a 48 -inch x 48 -inch concrete
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box culvert with a sluice gate, which will allow them to act as one interconnected pond or
operated individually if desired for maintenance.
The total storage volume of the Temporary Stormwater Ponds is approximately 20MG.
They are designed to hold the runoff from the 25- year — 24-hour design storm (6 -inches)
without overtopping. A pumping system will be constructed as the primary outlet for the
Temporary Stormwater Ponds, and it will be discharged to an existing NPDES permitted
stormwater outfall via a forcemain. The 12 -inch HDPE forcemain is approximately 7,000 -
ft in length and will be generally placed on the ground surface.
Each of the two pump stations will contain two 10hp pumps. These pumps are
significantly smaller than the pumps required for the pump stations considered for the
alternative pumping option since there is significant storage available for attenuation of
stormwater flows and pumping can be spread out over time.
The Temporary Stormwater Ponds will be operated for approximately 10 -years and
removed once the Ash Basin final cover is completed. The ponds will be removed and
the area will be backfilled with controlled compacted fill.
The total estimated cost for construction the Structural Fill Re-routing project, including
the swale, Temporary Stormwater Ponds, pump stations and forcemain is $28.1 MD,
according to estimates and bids prepared by Duke Energy. This cost does, however,
include the removal of the CCR from the Ash Basin in the project area. The removal of
CCR in this area was a planned part of the Ash Basin closure work to support lateral
expansions of the Industrial Landfill during the Ash Basin closure project. The CCR
dewatering, excavation, and backfilling with soil is estimated to be about $19.8 MD, so
the net cost for the stormwater management alternative selected to convey the
stormwater through a channel around the Structural Fill to the Temporary Stormwater
Ponds is then approximately $8.3 MD.
A comparison of the estimated construction and O&M costs for both the selected and
alternative stormwater management options is provided for the table below. A 100 -year
period was selected for comparison, however the construction and maintenance
associated with the pump stations, etc. for the pumping alternative option would continue
beyond the 100 -year period.
The projected construction costs are based upon the structure and equipment
replacement assumptions listed above. From the table below, the estimated total 100 -
year cost of the selected option is $21.8 MD, while the alternative pumping costs total
$96.1 MD.

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96.1 $ 21.80
In addition to the significant cost advantage of the selected option, the proposed re-
routing swale, Temporary Storage Ponds and forcemain represent a more reliable
system to successfully manage stormwater. The proposed alternative uses less fuel, has
minimal impact on air quality, and requires less maintenance. Once the Temporary
Storage Ponds are removed after approximately 10 -years of operation, no maintenance
or replacement of mechanical equipment is required. Maintenance of the swale and final
cover is conventional upkeep associated with grass lined or armored conveyances.
CrImment 4
In Section 4.3.2 (Pump Alternative) you state, "This action (referring to pumping the low
areas [i.e., jurisdictional wetlands and streams] adjacent to the ash basin) would
necessitate pumping in perpetuity which would lead to excess long-term O&M costs."
Please provide yearly O&M costs for the previously described action.
Response
The table above provides O&M costs associated with both the pump alternative and
gravity flow alternative. As stated in the previous response to Comment 3, the O&M
costs would be expected to occur beyond the 100 -year period, but the 100 -year period
was selected for the purposes of comparing the options.
Comment 5
In Section 4.3.3 (Structural Fill — Open Cut Channels Alternative), it does not seem this
alternative was fully analyzed. Could this alternative be combined, like the chosen
alternative, with temporary stormwater ponds which would be pumped to a new NPDES
permitted outfall? These potential stormwater ponds could be constructed and function
similar to the chosen alternative. Do this alternative (i.e., Open Cut Channel Alternative)
with the additional measures (i.e., pumped stormwater ponds) reduce or increase capital
costs and O&M costs compared to the chosen alternative (i.e., Gravity and Pump
Alternative)?
W
PUMP ALTERNATIVE
GRAVITY FLOW ALTERNATIVE
PROJECT
PROJECTED
PROJECTED
PROJECTED
PROJECTED
YEARS
CAPITOL
O&M COSTS
COMMENTS
CAPITOL
O&M COSTS
COMMENTS
COSTS(MD)
M❑
COSTS(MD)
(MD)
0-10
$ 20.10
$ 3.00
Initial Construction
5 8.3
$ 1.80
Inst al Construction - Temp
Ponds and Redirect Swale
11-20
$ 1.35
$ 3.00
Pump Replacement Year 15
$ 2.50
$ 1.20
Removal of Temp Storage
Ponds
Pump Station Year 33 and Pump
2140
$ 18.45
$ 6.00
Replacement Year 30
$ _
$ 2,00
Maintenance for Swale only
41 60
$ 5.05
$ 6.00
Pump Replacement Year 45 and
§
$ 2,00
Maintenance for Swale only
FM Replacement Year 50
61-60
5 1.35
$ 6.00
Pump Replacement Year 60
$
5 2.00
Maintenance for swale only
Pump Station Replacement Year
81-100
$ 19.80
$ 6.00
66 and Pump Replacement Year
$
$ 2.00
Maintenance for swale only
75.90
TOTAL
$ 66.1
1 $ 30.0
$ 10,801$
11.00
96.1 $ 21.80
In addition to the significant cost advantage of the selected option, the proposed re-
routing swale, Temporary Storage Ponds and forcemain represent a more reliable
system to successfully manage stormwater. The proposed alternative uses less fuel, has
minimal impact on air quality, and requires less maintenance. Once the Temporary
Storage Ponds are removed after approximately 10 -years of operation, no maintenance
or replacement of mechanical equipment is required. Maintenance of the swale and final
cover is conventional upkeep associated with grass lined or armored conveyances.
CrImment 4
In Section 4.3.2 (Pump Alternative) you state, "This action (referring to pumping the low
areas [i.e., jurisdictional wetlands and streams] adjacent to the ash basin) would
necessitate pumping in perpetuity which would lead to excess long-term O&M costs."
Please provide yearly O&M costs for the previously described action.
Response
The table above provides O&M costs associated with both the pump alternative and
gravity flow alternative. As stated in the previous response to Comment 3, the O&M
costs would be expected to occur beyond the 100 -year period, but the 100 -year period
was selected for the purposes of comparing the options.
Comment 5
In Section 4.3.3 (Structural Fill — Open Cut Channels Alternative), it does not seem this
alternative was fully analyzed. Could this alternative be combined, like the chosen
alternative, with temporary stormwater ponds which would be pumped to a new NPDES
permitted outfall? These potential stormwater ponds could be constructed and function
similar to the chosen alternative. Do this alternative (i.e., Open Cut Channel Alternative)
with the additional measures (i.e., pumped stormwater ponds) reduce or increase capital
costs and O&M costs compared to the chosen alternative (i.e., Gravity and Pump
Alternative)?
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Response
Open cutting of the Structural Fill to construct channels could be conveyed to temporary
stormwater ponds like the chosen alternative. However, the approximate 2.5 million tons
of ash that would require excavation to establish the open cut channels would need to
be disposed of in a permitted landfill based on requirements from NCDEQ, Division of
Waste Management, Solid Waste Section. The removal of the CCR and the placement
into a disposal facility requires regulatory approval through the Division of Waste
Management permitting process. The only practical permitted landfill for disposal would
be the on-site Industrial Landfill.
Currently the on-site Industrial Landfill has four (4) cells constructed and operational.
Based on the latest aerial survey of the landfill, there are approximately 2,357,000 cubic
yards (CY) of remaining airspace in Cells 1-4. Assuming a conversion rate of 1.2
tons/CY, approximately 2,083,333 CY of ash material excavated to establish the open
cut channels would need to be disposed of in the landfill. It is estimated that this could
conservatively be placed in the landfill at a rate of 50,000 CY/month based on
performance at other Duke Energy sites. This would equate to approximately 42 months
or 3.5 years. Per the Coal Ash Management Act (CAMA) (§ 130A -309.210.d) deadline,
this project must be completed by December 31, 2019 to eliminate these stormwater
discharges into the ash basin. To meet the deadline, ash excavation from the Structural
Fill would have to have started by July 1, 2016 at the latest if this activity could be
performed in parallel with other construction activities to meet the project end date. It
should also be noted that Cells 3 & 4 did not receive a Permit to Operate from NCDEQ
until April 18, 2018. Therefore, the approximate 14 -month long Cells 3 & 4 construction
project would have to have been completed between May 1, 2015 and July 1, 2016.
CAMA placed a moratorium on the expansion and construction of coal combustion
residuals landfills until August 1, 2015. Therefore, the Cells 3 & 4 construction project
schedule would have to have been compressed to meet the July 1, 2016 date to start
receiving ash, which would have likely resulted in a cost increase to the overall project.
Additionally, with the Structural Fill ash excavation consuming the majority of the Cells 1-
4 airspace, future Cells 5 & 6 would have to be constructed to continue to support the
disposal of ash generated from burning coal at the station. Cells 5 & 6 would provide
approximately 3.5 million CY of additional airspace. While Cells 5 & 6 were permitted
through NCDEQ for Site Suitability, Cells 5 & 6 would still require a Permit to Construct
from NCDEQ. The engineering design and permitting timeframe is estimated to be
around two (2) years to receive a Permit to Construct from NCDEQ. In addition, it would
be another 14 months of construction (similar to Cells 3 & 4) to construct Cells 5 & 6.
Whether the excavated ash from the Structural Fill was placed in Cells 3 & 4
(approximate 16 -acre footprint) or Cells 5 & 6 (approximate 18 -acre footprint), a lateral
expansion of about 17 acres would be necessary to support the disposal of this ash
excavated from the Structural Fill. This would result in about a $27 million (M) capital
cost increase to construct the new liner system for the lateral expansion and dispose of
the ash in the new landfill cells. Additionally, operations and maintenance (O&M) costs
would be expected to increase by about $50,000 per year due to the increased landfill
footprint. This O&M cost would be incurred until the entire landfill was permanently

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closed and the 30 -year post -closure period is complete. This would be for an assumed
65 -year duration resulting in a $3.25M total O&M cost.
There are no other areas on the Marshall Steam Station site suitable for development of
a disposal facility to accept the CCR removed from the Structural Fill.
In summary, this option is infeasible since compliance with existing governing
regulations cannot be maintained and there are no practical alternatives for disposal of
this material on the project site.
Did you coordinate with the North Carolina Department of Environmental Quality,
Division of Mitigation Services (NCDEQ-DMS) to verify if stream and wetland credits
were available for purchase through the In -Lieu Fee Program? If so, please provide a
copy of the letter received from NCDEQ-DMS stating they are willing to accept payment
for compensatory mitigation for stream and wetland impacts associated with the
proposed project.
Response
Duke Energy coordinated with the NCDEQ-DMS for the purchase of mitigation credits
(In -Lieu Fee Program) for the proposed impacts to jurisdictional wetlands and streams
on the Marshall Steam Station Stormwater Redirection Project at the Marshall Plant. The
Conditional Acceptance Letter (dated August 30, 2018) from the NCDEQ-DMS is
attached herein. Please note that the mitigation credit purchase reflects the change to
the mitigation ratio for Wetlands D, E, F, and G (see Comment 7 below), as well as the
NCDEQ Current Rate Schedules for streams and wetlands (as of July 1, 2018) (see
Comment 8 below).
Comment 7
The compensatory mitigation ratio (1:1) for Wetlands D, E, F, and G, is not sufficient to
offset the environmental losses resulting from the unavoidable impacts to the previously
mentioned wetlands within the proposed project area. Compensatory mitigation must be
commensurate with the amount and type of impact. The proposed project plans to
impact all four wetlands (0.55 acres) in their totality, resulting in a loss of over 90 percent
of wetlands within the proposed project area. A wetland quality assessment form (i.e.,
North Carolina Wetland Assessment Method) was conducted to determine the level of
function of a wetlands within the proposed project area relative to reference condition. A
ratio of less than 2:1 is justified based on the lower quality of the impacted wetlands.
Therefore, the Corps proposes a compensatory mitigation ratio of 1.5:1 for Wetlands D,
E, F, and G. Please revise your Compensatory Mitigation Plan to reflect this change in
compensatory mitigation ratio for Wetlands D, E, F, and G.
Response
Duke Energy will comply with the USACE proposal to establish a compensatory
mitigation ratio of 1.5:1 for the proposed impacts to Wetlands D, E, F, and G. The
11

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Compensatory Mitigation Plan for the Marshall Steam Station Stormwater Redirection
Project has been accordingly revised to reflect this change in the mitigation ratio for
Wetlands D, E, F, and G, as shown in the revised Table 10 (from the Wetland Master
Plan) in the response to Comment 8 below.
Comment 8
Please revise Table 10 (Potential mitigation costs for impacts to waters of the U.S.) to
represent the current North Carolina, Department of Environmental Quality's Current
Rate Schedules for streams and wetlands. As of July 1, 2018, the cost for one linear foot
of stream credit is $507.32 and $104,447.63 for one acre of wetland (riparian and
nonriparian) credit within the Catawba service area (HUC 03050101). Therefore, based
on the newly revised Current Rate Schedule, the proposed project compensatory
mitigation costs would be as follows: a). Streams 7, 10, and 11 = $380,490; b). Streams
8 and 9 = $486,013; and c). Wetlands D, E, F, and G = $78,336; for a total of $944,839.
This total was generated by calculating the stream credits for Streams 7, 10, and 11 at a
ratio of 1.5:1 and Streams 8 and 9 at a ratio of 2:1 and 0.75 acre of wetland credit.
Response
Table 10 (from the Wetland Master Plan) for the Marshall Steam Station Stormwater
Redirection Project has been revised accordingly to reflect the NCDEQ Current Rate
Schedules for streams and wetlands (as of July 1, 2018). The revised Table 10 is
presented below. Please note that the aforementioned fee of $78,336 for Wetlands D, E,
F, and G that was identified by the USACE reflects a mitigation ratio of 1:1. However, as
based on the compensatory mitigation ratio of 1.5:1 that was proposed by the USACE
for these four wetlands (see Comment 7), the fee would be $86,170. In addition, the
NCDEQ-DMS is no longer rounding to the quarter acre on invoices; therefore, the 0.55
acre wetland impact value would not be rounded to the 0.75 acre higher increment for
the credit cost calculation. Furthermore, the NCDEQ-DMS does not have non -riparian
wetland credit available in the service area that the Marshall Steam Station Stormwater
Redirection Project occurs within. In accordance with the directive from the February 8,
2011 IRT meeting, non -riparian wetland impacts located in the mountains and piedmont
areas of North Carolina can be accepted as requested, but mitigated utilizing riparian
wetland mitigation credits. The NCDEQ-DMS can accept payment for the non -riparian
wetland impact, but are offering to debit riparian wetland credits. Finally, the Marshall
Steam Station Stormwater Redirection Project occurs within the Hydrologic Unit Code
(HUC) 03050101, in the Catawba River Basin. The Catawba HUC 03050101 is now
considered a Premium rate area and has a higher rate.
The total fee for all project related wetland and stream impacts from the construction of
the Marshall Steam Station Stormwater Redirection Project would be $952,673, rather
than the value of $944,839 as identified by the USACE.
12

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Table 10. Updated mitigation costs for impacts to waters of the U.S., Stormwater
Redirection Project, Marshall Steam Station, Catawba County, North
Carolina.
NCWRC
Comment 1
If active bald eagle nests occur within the vicinity of the Marshall Steam Station,
coordination with the USFWS may be required to avoid impacting bald eagles,
particularly during the construction. Further information on the National Bald Eagle
Management Guidelines can be found at
https://www.fws.gov/northeast/ecologicalservices/eaglenationalguide.html. The USFWS
can be contacted at [phone] to ensure that potential issues related to bald eagles
are addressed.
Response
Duke Energy acknowledges the above comment regarding coordination with the
USFWS if active bald eagle nests are discovered within the vicinity of the Marshall
Steam Station, as related to the effect that the project may have on the species,
particularly during construction.
Comment 2
For surface waters not impacted by the project, maintain a minimum 100 -foot
undisturbed, native, forested buffer along perennial streams, and a minimum 50 -foot
buffer along intermittent streams and wetlands. Maintaining undisturbed, forested buffers
along these areas will minimize impacts to aquatic and terrestrial wildlife resources,
water quality, and aquatic habitat both within and downstream of the project area. Also,
wide riparian buffers are helpful in maintaining stability of stream banks and for
treatment of pollutants associated with urban stormwater.
13
NCDMS In-
Total
Fee Category
Features
Impact Total
Lieu Fee
Cost ,
Unit Cost
Riparian and
Wetlands D, E, and F
Non -riparian
(Riparian) and Wetland
0.55 acre
$104,447.63
$86,170
Wetlands
G (Non -riparian)
(1.5:1 ratio)
(per acre)
NC WAM Low Rating)
Intermittent
Streams 7, 10, and 11
500 linear feet
$507.32
Streams
(NC SAM Low and
(1.5:1 ratio)
(Per linear
$380,490
Medium Ratings)foot
Perennial
Streams 8 and 9
479 linear feet
$507.32
(Per linear
$486,013
Streams
(NC SAM High Rating)
(2:1 ratio)
foot)
Total
$952,673
NCWRC
Comment 1
If active bald eagle nests occur within the vicinity of the Marshall Steam Station,
coordination with the USFWS may be required to avoid impacting bald eagles,
particularly during the construction. Further information on the National Bald Eagle
Management Guidelines can be found at
https://www.fws.gov/northeast/ecologicalservices/eaglenationalguide.html. The USFWS
can be contacted at [phone] to ensure that potential issues related to bald eagles
are addressed.
Response
Duke Energy acknowledges the above comment regarding coordination with the
USFWS if active bald eagle nests are discovered within the vicinity of the Marshall
Steam Station, as related to the effect that the project may have on the species,
particularly during construction.
Comment 2
For surface waters not impacted by the project, maintain a minimum 100 -foot
undisturbed, native, forested buffer along perennial streams, and a minimum 50 -foot
buffer along intermittent streams and wetlands. Maintaining undisturbed, forested buffers
along these areas will minimize impacts to aquatic and terrestrial wildlife resources,
water quality, and aquatic habitat both within and downstream of the project area. Also,
wide riparian buffers are helpful in maintaining stability of stream banks and for
treatment of pollutants associated with urban stormwater.
13

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ENERGY.
Response
Duke Energy acknowledges the above comment regarding the establishment of a
undisturbed, native, forested buffer along streams and wetlands to minimize impacts to
aquatic and terrestrial wildlife resources, water quality, and aquatic habitat both within
and downstream of the project area. Riparian buffers will be established to the extent
practicable. The locations and widths of riparian buffers post -construction will be
determined based on project configuration and utility.
Comment 3
Avoid tree clearing activities during the maternity roosting season for bats (May 15 —
August 15).
Response
Please see the response to USACE Comment 1 to address this NCWRC
recommendation.
CnmmPnt 4
Water discharges from the site should be proportional to the size of the receiving stream
so the hydrology of the stream is not altered, and all discharges should comply with
NPDES permit requirements. In particular, turbidity of the discharge should be
maintained at or below the permit requirement. High water discharge rates and turbidity
can negatively impact aquatic resources within and downstream of the site. Excessive
silt and sediment loads can have numerous detrimental effects on aquatic resources
including destruction of spawning habitat, suffocation of eggs, and clogging of gills of
aquatic species.
Response
All development projects in North Carolina that disturb an acre or greater of land require
an approved Erosion & Sediment Control (E&SC) Plan. E&SC Plans must be produced
in accordance with the North Carolina Erosion and Sediment Control Planning and
Design Manual, dated May 2013. This manual includes best management practices
(BMPs) for reducing erosion and sedimentation during construction. This requires proper
site preparation techniques, surface stabilization, runoff control measures, diffuse flow
through the riparian buffer, inlet and outlet protection, and stream protection. The E&SC
Plan for the Marshall Steam Station Stormwater Redirection Project will include methods
to minimize water run-off from the site. All discharges from the project site will comply
with permit requirements. No contact water (i.e., water in contact with CCR materials)
will be discharged into waters of the U.S. (wetlands and streams); therefore, the water
quality of downstream receiving waters will not be impaired. In addition, opportunities for
the degradation of aquatic resources within and downstream of the project site (via high
water discharge rates or turbidity) will be minimized under the E&SC Plan.
14

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TOT, �71", Uri W,
Consider using native seed mixtures and plants that are beneficial to wildlife for
revegetating disturbed areas, specifically seed mixtures that create pollinator habitat.
Avoid using Bermudagrass, redtop, tall fescue, and lespedeza, which are invasive
and/or non-native and provide little benefit to wildlife. Consider an alternative mix of red
clover, creeping red fescue, and a grain, such as oats, wheat, or rye.
Response
The suggested plant mixes for both temporary and permanent seeding will be identified
on the Marshall Steam Station Stormwater Redirection Project engineering drawings,
including the Erosion and Sedimentation Control Plan (E&SC Plan). The seeding
specifications will be based on standard and appropriate horticultural guidelines for
seeding construction sites. However, the recommendations provided by the NCWRC will
be taken into consideration.
Sediment and erosion control measures should use advanced methods and installed
prior to any land -disturbing activity. The use of biodegradable and wildlife -friendly
sediment and erosion control devices is strongly recommended. Silt fencing, fiber rolls
and/or other products should have loose -weave netting that is made of natural fiber
materials with movable joints between the vertical and horizontal twines. Silt fencing that
has been reinforced with plastic or metal mesh should be avoided as it impedes the
movement of terrestrial wildlife species. Excessive silt and sediment loads can have
detrimental effects on aquatic resources including destruction of spawning habitat,
suffocation of eggs, and clogging of gills.
Response
Sediment and erosion control measures will be identified in the E&SC Plan. Project
activities for the Marshall Steam Station Stormwater Redirection Project will be
conducted in a manner to minimize the potential for erosion and sedimentation.
Sediment and erosion control measures shall be installed prior to land -disturbing
activities in accordance with the E&SC Plan. The E&SC Plan includes re -seeding
schedules and methods to minimize sediment discharge from the site. The
recommendations provided by the NCWRC will be taken into consideration.
Thank you in advance for your assistance with this project. If you have any questions or
need additional information, please contact me at telephone number [phone] or
email address steve.cahoon(ab-duke-energy.com.
15

Sincerely,
Steve Cahoon
Enclosures
Cc: Sue Homewood (NCDEQ DWR)
Byron Hamstead (USFWS)
Olivia Munzer (NCWRC)
Kyle Baucom (Duke Energy)
Richard Harmon (Wood)
16
DUKE
ENERGY.,

Mtt/g[ttivn,ervlces
EW VIROMMENTALQUAL1TV
August 30, 2018
Steve Cahoon
Duke Energy Carolinas, LLC
410 S. Wilmington St
Raleigh, NC 27601
This is a conditional acceptance letter.
Project: Marshall Steam Station Stormwater Redirection Project
ROY COOPER
Governor
MICHAEL S. REGAN
.Secretary
Expiration of Acceptance: 3/2/2019
County: Catawba
The purpose of this letter is to notify you that the NCDEQ Division of Mitigation Services (DMS) is willing to
accept payment for compensatory mitigation for impacts associated with the above referenced project as
indicated in the table below. Please note that this decision does not assure that participation in the DMS in -
lieu fee mitigation program will be approved by the permit issuing agencies as mitigation for project impacts.
It is the responsibility of the applicant to contact permitting agencies to determine if payment to the DMS will
be approved. You must also comply with all other state, federal or local government permits, regulations or
authorizations associated with the proposed activity including G.S. § 143-214.11.
This acceptance is valid for six months from the date of this letter and is not transferable. If we have not
received a copy of the issued 404 Permit/401 Certification within this time frame, this acceptance will
expire. It is the applicant's responsibility to send copies of the permits to DMS. Once DMS receives a copy
of the permit(s) an invoice will be issued based on the required mitigation in that permit and payment must
be made prior to conducting the authorized work. The amount of the in -lieu fee to be paid by an applicant is
calculated based upon the Fee Schedule and policies listed on the DMS website.
Based on the information supplied by you in your request to use the DMS, the impacts for which you are
requesting compensatory mitigation credit are summarized in the following table. The amount of mitigation
required and assigned to DMS for this impact is determined by permitting agencies and may exceed the
impact amounts shown below.
River Basin Impact Location
I (8 -digit HUC)
Catawba � 03050101
Impact Type
Warm Stream
Riparian Wetland
Non -Riparian Wetland*
Impact Quantity
979
0.16
0.39
*DMS does not have non -riparian wetland credit available in this service area. In accordance with the
directive from the February 8, 2011 IRT meeting, non -riparian wetland impacts located in the
mountains and piedmont areas of North Carolina can be accepted as requested, but mitigated
utilizing riparian wetland mitigation credits. Upon receipt of payment, DMS will take responsibility for
providing the compensatory mitigation. The mitigation will be performed in accordance with the In -Lieu Fee
Program instrument dated July 28, 2010. Thank you for your interest in the DMS in -lieu fee mitigation
program. If you have any questions or need additional information, please contact Kelly Williams at (919)
707-8915.
cc: Richard Harmon, agent
Sincerely,
Jane . B Stanfill
As t anagement Supervisor
State of North Carolina I Environmental Quality I Mitigation Services
1652 Mail Service Center I Raleigh, NC 27699-1652 1 217 W. Jones Street, Suite 3000
919 707 8976 T