NCS000548_Duke Energy Marshall Temp SW Pond Permit Mod Info_20180618

AECOM March 16, 2018
Duke Energy — Marshall Steam Station
Temporary Stormwater Ponds Application — MAR -145 Area
6. ENVIRONMENTAL PERMITTING
6.1 Permit Modifications
6.1.1 Solid Waste Permit Modifications
No Solid Waste permit is in place for the Ash Basin. Closure of the Ash Basin will require
review and approval by NCDEQ, including the Division of Waste Management. No Permit
Modifications have been identified to complete the proposed Partial Closure.
6.1.2 NPDES Permit Modifications
Prior to the modification of any existing stormwater discharge, Duke Energy will submit a
NPDES stormwater permit modification application to NCDEQ. Prior to development of any new
stormwater discharge, Duke Energy will submit a NPDES stormwater permit application to
NCDEQ.
6.1.3 Air Permit Modifications
A modification to the Air Permit will not be required to complete the Partial Closure. Dust control
measures currently employed for the Ash Basin operations will be continued during the Partial
Closure.
6.2 New Permits
6.2.1 Clean Wafer Act Section 4041401
As set forth in 33 CFR 328.3(b)(1), amended by the Clean Water Rule, Clean Water Act Section
4041401 permit requirements do not apply to the Ash Basin because they are considered
exempt waste treatment systems. However, a United States Army Corps of Engineers
(USAGE) Section 404 permit will still be necessary for impacts to Waters of the US or
jurisdictional wetlands adjacent to the Ash Basin during Partial Closure activities, including
excavation, stormwater diversion and construction of the Temporary Stormwater Ponds. A
Section 404 permit may also be required to construct the stormwater diversion around the
Structural Fill since fill may be placed within jurisdictional areas to establish the required grades
to properly manage stormwater. An individual permit will be applied for with the USACE and
NCDEQ DWR 401 Water Quality Permitting Section, but is not part of the scope of this
Application.
6.2.2 Federal Energy Regulatory Commission Approval
Requirements set forth in the Duke Energy Catawba-Wateree Shoreline Management Plan will
be met. As required by the Federal Energy Regulatory Commission (FERC) Catawba-Wateree
Project License P-2232, issued November 25, 2015, approval for any placement of fill into Lake
Norman will be obtained by FERC prior to commencing closure construction activities. No such
activities are included in the scope of the Partial Closure.

AECOM May 7, 2018
Duke Energy — Marshall Steam Station
Structural Fill Stormwater Diversion Channel Application — MAR -145
5. ENVIRONMENTAL PERMITTING
5.1 Permit Modifications
5.1.1 Solid Waste Permit Modifications
The Structural Fill is a permitted CCR management facility (NCDEQ Permit #CCB0031) and
modification of the limits or the final cover of the Structural Fill will require a Permit Modification.
A major modification is not anticipated since the lateral and vertical extents and the capacity of
the Structural Fill will not be amended as part of the proposed work.
5.1.2 NPDES Permit Modifications
Prior to the modification of any existing or development of a new stormwater discharge, Duke
Energy will submit a NPDES stormwater permit modification application to NCDEQ. Since the
quantity, quality or discharge location of the stormwater to be managed will not be modified by
the proposed work, no modification of stormwater outfalls are proposed. Any new stormwater
discharges will be included in the scope of the Temporary Stormwater Ponds, which is
addressed in a separate Application.
5.1.3 Air Permit Modifications
A modification to the Air Permit will not be required to complete construction of the Structural Fill
Redirection Stormwater Channels.
5.1.4 Dam Safety
Construction of the Structural Fill Redirection Stormwater Channels does not require Dam
Safety permitting since the Ash Basin Dam is not impacted by the construction and the channels
do not impound water.
5.2 New Permits
5.2.1 Floodplain Development
None of the Structural Fill Redirection Stormwater Channel work area is located within the 100 -
year floodplain, as shown on panel 3710461800J of the National Flood Insurance Program
(NFIP) Flood Insurance Rate Map (FIRM). No floodplain development permitting will be
required for the proposed Structural Fill Redirection Stormwater Channels.
5.2.2 NPDES Permit for Construction Activities
Because land disturbance associated with construction of the Structural Fill Redirection
Stormwater Channels, will exceed one acre, installation of erosion and sediment control
measures and a submittal of an Erosion and Sedimentation Control Plan will be conducted in
conformance with 15A NCAC 04, the NCDEQ Erosion and Sediment Control Planning and
Design Manual, and Catawba County Code of Ordinances Chapter 31.