Riverbend Steam Station (2)

NCDENR
North Carolina Department of Environment and Natural Resources
Beverly Eaves Perdue
Governor
Mr. Allen Stowe
Water Management
Duke Energy Corporation
EC13K/ P.O. Box 1006
Charlotte, North Carolina 28201 -1006
Dear Mr. Stowe:
Division of Water Quality
Coleen H. Sullins
Director
September 7, 2010
Subject: NPDES Stormwater Permit Application
Marshall, Allen, and Riverbend Steam Stations
Duke Energy Carolinas, LLC
Catawba and Gaston Counties
Dee Freeman
Secretary
On August 12, 2010, we discussed with you questions about application materials for a separate NPDES
stormwater permit for the Marshall Steam Station plant. The information you submitted included a sample
from only one stormwater outfall (SW 007); however Section 4.0 of your application indicated a total of 11
stormwater discharge outfalls (SDOs).
You explained that a previous arrangement with DWQ's NPDES Permitting Unit led to the direction of
submitting EPA Form 2F with your discharge permit renewal application. Further, an agreement with
NPDES permitting staff established SW 007 at Marshall Steam Station as "representative" for the purpose of
rompleting the stormwater portion of your renewal application.
You provided a site map and narrative descriptions of the drainage areas for each stormwater outfall at the
Marshall site. However, the information was somewhat unclear about which stormwater outfalls were
separate from NPDES wastewater outfalls. For example, SW 007 is also described as'NPDES Outfall 002A.'
Information indicates emergency sump overflow would also route through this outfall. If this outfall is
normally a stormwater discharge and rarely a wastewater discharge, please describe how often and under
what conditions sump overflow occurs. Also, you expressed concern in our phone discussion that regional
office staff sirggled out some stormwater drop inlets on site that ultimately drain to wastewater treatment.
It was unclear whether these involved any of the 11 SDOs identified in your application information.
To continue proc: ;sing your application for an individual NPDES stormwater permit, please provide the
following additio;—1 information by October 8, 2010:
List of which stormwater outfalls discharge only stormwater to surface waters
• Information about the frequency of emergency sump overflows that discharge to SDOs (or other
wastewater that may discharge through SDOs and how often)
Wetlands and Stormwater Branch
1617 Mail Service Center, Raleigh, North Carolina 27699 -1617
Location: 512 N. Salisbury St. Raleigh. North Carolina 27604 One 1
Phone: [phone] FAX. [phone] Customer Service: 1- 877 -623 -6748 Nort L. lCarOl111a
Internet: www.ncwaterquality.org
An Equal Opportunity 1 Affirmative Action Employer Naturally

Mr A Stowe
Duke Energy Corp
September 7, 2010
Page 2
We will need the same information "for the Allen and Riverbend Steam Station applications, as well as any
stormwater sample results from those sites that are available We will proceed with permit development
for the Marshall site based on the stormwater sampling from SW 007 already provided
Please note that NPDES stormwater permits typically require sampling for each stormwater discharge
outfall-(SDO) However, the facility will have the opportunity to request Representative Outfall Status
('ROS') for a subset of outfalls after the permit is issued and more sample data are available. If approved by
the regional office, only overalls with ROS would need to be sampled (however, qualitative /visual
monitoring would still appix, to all outfalls) A form for,requesting ROS is available on our website under
the "Application Forms" tab here
http / /portal ncdenr org.jwebAvq/ws/su.ZnDdessw
If you have any questions cr comments concerning this letter, contact me at (919) 807 -6372 or
bethany georgouliasOncdenr go v, or Bradley Bennett at (919) 807 -6378 or bradley bennett@ncdenr gov
Sincerely,
Beth ny A eorgoulias
Environmental Engineer
Stormwater Permitting Unit
cc Mooresville Regional Office, Water (duality Section
Stormwater Permitting Unit
NPDES Wastewater Permitting / Sergei Chernikov
E
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