20150717 Ver 2_RAI response_20170508

Mr. David E. Bailey August 26, 2015
Project Manager
US Army Corps of Engineers
CE -SAW -RG -R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
RE: Response to Request for Additional Information
US Army Corps of Engineers Permit No. SAW -2015-01670
Duke Energy Dan River Stream Station
Eden, Rockingham County, NC
48 -inch Culvert Inlet Area Clean -Up
Dear Mr. Bailey:
Duke Energy, in consultation with Amec Foster Wheeler, Environment & Infrastructure,
Inc. (Amec Foster Wheeler), submitted a Pre -Construction Notification (PCN) to the
Raleigh Regulatory Field Office of the US Army Corps of Engineers (USACE) for
issuance of Nationwide Permit (NWP) 18 for the 48 -inch Culvert Inlet Area Clean -Up
project at the Dan River Steam Station, Eden, Rockingham County (PCN dated July 17,
2015). Subsequent to your review of the PCN, you presented five remarks and/or
requests for additional information (RAI) in correspondence, dated July 31, 2015, to
Duke Energy and the attention of Mr. Steve Cahoon. As enumerated herein for
discussion purposes, these five items and the respective responses are presented
below.
Item Number 1
The PCN includes impacts to stream and wetlands related to inundation. However, the
PCN does not include information regarding the discharge of dredged or fill material in
wetlands or other waters of the US that triggers a CWA section 404 permit. Please add
plans/design sheets and update section C of the PCN that clearly describe the regulated
activity.
Response
A 0.003 -acre (144 square feet) fill impact to waters of the US is now included under the
proposed action to backfill around a sump for the pumping system. This fill impact,
which will occur within the lowest portions of the wetland nearest to the abandoned 48 -
inch pipe (i.e., Wetland 1), is required to facilitate the diversion of storm water flows from
the area upstream of this point to another surface water discharge at the Service Water
Settling Basin impoundment which discharges to the Dan River upstream of the
powerhouse dam. The location of the proposed concrete drop inlet is depicted in the
updated Plan View drawing, which is attached herein. A Cross -Section View drawing of
the concrete drop inlet is also attached herein. Finally, Section C of the PCN form has
been updated to reflect the aforementioned activities and further describe the regulated
activity. The revised PCN form is attached herein.
Accumulated ash from the February 2, 2014 release will be removed from the wetland
and upland areas by skimming off the upper layer of ash and soil mix and reseeding the

area. This latter activity may necessitate the backfill of soils as based on the depth of
removal of the accumulated ash.
Item Number 2
Section B.3d. of the PCN ties the purpose of the proposed project to the ash pond clean-
up. Note that this office is currently reviewing a proposal at the Dan River Steam Station
to expand a railroad line to dispose of coal ash on site (SAW -2015-01381). We will
review all projects related to coal ash clean up as part of the same single and complete
project. Based on NWP condition 28, and the definitions of "single and complete project"
and "independent utility" found in the NWP terms and conditions, please justify how this
proposed project is single and complete, and why it should not be considered cumulative
with the coal ash removal/disposal activities on site and the previously authorized 36"
culvert plug project (SAW -2014-01477).
Response
The purpose of the 48 -inch Culvert Inlet Area Clean -Up project is to provide for the
clean-up of the accumulated ash from the pipe failure and to divert the temporary
impoundment of stormwater at the grouted 48 -inch CMP. The project was developed to
respond to the Coal Ash Management Act, as an effort to clean up deposited ash after
the failure of the 48 -inch culvert and keep stormwater out of the basin. The proposed
project preceded, and is not related to, the proposal to expand the railroad line at the
Dan River Steam Station to facilitate the disposal of coal ash from the station. To
summarize, the proposed action under SAW -2015-01381 for the expansion of the
railroad line to dispose of coal ash is presumed to represent a separate project, as it
specifically relates to the disposal of coal ash and is not associated with the temporary
impoundment of stormwater, or the prevention of stormwater flow under the ash fill basin
(i.e., as related to the 36 -inch Culvert Plug project and the 48 -inch Culvert Inlet Area
Clean -Up project).
The purpose of the permitted 36 -inch Culvert Plug project was to plug an existing 36 -
inch diameter reinforced concrete culvert to prevent water from flowing under the ash fill
basin. The purpose/proposed actions of the 36 -inch Culvert Plug project and the 48 -inch
Culvert Inlet Area Clean -Up project are not identical. However, the USACE, Raleigh
Regulatory Field Office, issued NWP 18 for the 36 -inch Culvert Plug project (SAW -2014-
01477) with the following Special Condition 2: "Please note that future phases of pipe
closures and other coal ash basin cleanup activities at the Duke Energy Dan River
Steam Station may be considered part of a single and complete project, and impacts
may be considered cumulative, with respect to compensatory mitigation and Nationwide
Permit thresholds, with impacts permitted during earlier phases authorized and
documented under Action ID: SAW -2014-01477." The permittee recognizes that the
impacts to jurisdictional waters of the US for the 48 -inch Culvert Inlet Area Clean -Up
project may be considered by the USACE to be cumulative with the impacts to
jurisdictional waters of the US that were authorized under SAW -2014-01477 for the 36 -
inch Culvert Plug project. As such, compensatory mitigation for both projects may be
considered in a cumulative manner.
Item Number 3
Please note that, assuming comment 2 is addressed above, items currently listed in
PCN section C.2a and C.2b would be considered permanent impacts rather than

temporary, similar to the previously authorized 36" culvert plug project (SAW -2014-
01477).
Response
Section C.2a (wetland impacts) and section C.3a (stream impacts) of the PCN have
been revised to indicate that the proposed impacts to jurisdictional waters of the US for
the 48 -inch Culvert Inlet Area Clean -Up project will be permanent with respect to impact
type. The revised PCN is attached herein.
Item Number 4
A waiver of the stream impact threshold is requested based on Regional Condition 3.1.
However, the NCDWQ Stream ID Forms included with the PCN do not pertain to the
streams proposed for inundation (based on the latitude and longitude on the forms) and
document the features as being perennial instead of intermittent. Please submit
NCDWQ Stream ID Forms for the streams proposed for inundation to document an
intermittent flow regime.
Response
The NCDWQ Stream ID Forms for the three streams that are proposed for inundation for
the 48 -inch Culvert Inlet Area Clean -Up project are attached herein. These forms have
been revised to reflect a stream classification status of intermittent. The
latitude/longitude location data for the three streams, as reported on the forms, have
been verified.
Item Number 5
A reduced mitigation ratio of 1:1 is proposed for both wetland and stream inundation
impacts. Compensatory mitigation proposals should be based on aquatic function.
Further, as documented in the Wilmington District Public Notice dated 4/21/2015, the
Corps of Engineers Wilmington District will use the NC Wetland Assessment Method
(NCWAM) and the NC Stream Assessment Method (NCSAM) to evaluate aquatic
resource quality and functions for decisions regarding the amount and type of
compensatory mitigation.
<http://www.saw.usace.army.mil/Missions/RegulatoryPerm itProgram/PublicNotices/tabid
/10057/Article/5
85625/implementation-of-nc-sam-and-nc-wam.aspx>
Please submit NCWAM and NCSAM forms for the wetland and stream areas proposed
for inundation to justify your proposed reduced mitigation ratio of 1:1. Although these
forms are referenced in the PCN document, they were not included in the submittal
package. Please note that the USACE "Stream Quality Assessment Worksheet„ has
been replaced by the NCSAM form for documenting aquatic resource quality and
functions.
Response
The completed NC Stream Assessment Method (NCSAM) forms for Stream 1, Stream 2,
and Stream 3 for the 48 -inch Culvert Inlet Area Clean -Up project are attached herein.

The NC Wetland Assessment Method (NCWAM) forms for Wetland 1 and Wetland 2 for
the 48 -inch Culvert Inlet Area Clean -Up project are attached herein
Thank you in advance for your assistance with this project. If you have any questions or
need additional information, please contact Richard Harmon of Amec Foster Wheeler at
[phone] or at [e-mail].
Sincerely,
Steve Cahoon
Enclosures
Cc: Richard Harmon
Josh Bell
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