NC0004774_Outfall 007 Modification Request_20200413

f' DUKE Buck Combined Cycle Station
1385 Dukeville Rd.
ENERGY® Salisbury, NC 28146
April 2, 2020
Ms. Julie Grzyb
North Carolina Department of Environmental Quality
Division of Water Resources
1617 Mail Service Center �1���
Raleigh, NC 27699-1617 `- C
APR 137010
Subject: Buck Combined Cycle RINppES
NPDES Permit NC0004774 ‘4CDEwlpW
Permit Modification Request
Dear Ms. Grzyb:
In addition to the items requested in the March 20, 2020 subject letter (attached), it is
requested that the permit also be modified to increase the flow restriction for outfall 007.
With the need to ensure ash basin closure and the management of stormwater that
flows into the ash basin, the site WWTS consultants (Evoqua Water Technologies LLC)
have indicated that the dewatering treatment system has a capacity of 1.2 mgd. To
allow for a margin of safety it is therefore requested that the flow limitation be increased
from 0.72 mgd to 1.1 mgd for,outfall 007.
If you have questions, please contact Robert Wylie at [phone] or
[e-mail].
Sincere! ,
Kris Eisenrieth, General Manager II
Buck Combined Cycle
cc: Roberto Scheller. •
Attachment:
March 20, 2020 Permit Modification Request
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DUKE Buck Combined Cycle Station
-t-;:" ENERGY 1385 Dukeville Rd.
Salisbury, NC 28146
March 20, 2020
Ms. Julie Grzyb
North Carolina Department of Environmental Quality
Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Buck Combined Cycle
NPDES Permit NC0004774
Permit Modification Request
Dear Ms. Grzyb:
By this letter, Duke Energy Carolinas, LLC requests a modification of NPDES Permit
NC0004774. The following provides more information associated with this request.
With the start and completion of decanting activities for the ash basin, outfall 002 no
longer discharges. Pages associated with decanting for outfall 007 are no longer
applicable. Therefore, it is requested that references and the pages associated to
outfall 002 and outfall 007 (for decanting) be eliminated. Based on the recent
operations it has been determined that outfall 006 is no longer warranted. Outfall 006
has not been built and it has been determined that Outfall 001A can serve as the
compliance outfall for the combined cycle station. Therefore, it is requested that outfall
006 also be removed from the NPDES permit in this modification. Attachment 1
identifies these pages and paragraphs to highlight these changes.
During the decanting operation of the ash basin it was determined that a wastewater
treatment system was warranted in order to adjust the pH and to filter the solids. This
system has been put in place. The system uses acid and caustic addition to adjust pH.
It also has sand filters to remove any solids prior to being discharged from NPDES
outfall 007. With the presence of algae in the ash basin Duke Energy intends to use
sodium hypochlorite to maintain the filters free of biological growth. The company plans
to add the sodium hypochlorite upstream of the sand filters and maintain approximately
a 1 ppm free available chlorine concentration leaving the filters. The wastewater will be
treated with sodium bisulfite prior to outfall 007 in order to remove the chlorine. There
are current signs of algae forming in the ash basin. Therefore, it is requested that prior
to the NPDES permit being modified that the use of sodium hypochlorite and sodium
bisulfite be allowed as a trial to assure the efficacy of this algae control method and for
prevention of filter fouling. During a treatment trial period, Duke will conduct weekly
testing for TRC if necessary, in addition to the monthly toxicity testing already
conducted on this outfall. A check in the amount of$1,030 is being submitted directly to

Ms. Julie Grzyb
North Carolina Department of Environmental Quality
Division of Water Resources
March 20, 2020
Raleigh, NC 27699-1617
your office. If you have questions, please contact Robert Wylie at [phone] or
[e-mail].
Sincerely,
Kris Eisenrieth, General Manager II
Buck Combined Cycle
cc: Roberto Scheller
Attachments:
1. Itemized permit change requests
Raleigh
Mailed by USPS: 7019 0140 0001 0794 2511
Return Receipt USPS: 9590 9402 5350 9154 1977 15
Email to Roberto Scheller

Attachment 1
NPDES PERMIT CHANGES

Itemized Changes for NPDES Permit Modification Request for
Permit NC0004774
1. Update supplemental information on page ii.
2. Table of Contents has several line items to be deleted that include outfalls 002 and
006. Since 007 is now into dewatering references for decanting can be deleted.
3. Remove entire pages 1, 2, 3 and 4 for outfall 002
4. Remove entire pages 7 and 8 for outfall 006
5. Remove entire page 9 for outfall 002A, except for item A.(6).
6. Remove entire pages 11, 12,13 and 14 for outfall 002
7. Remove entire pages 15 and 16 for outfall 007.
8. Page 24 item C.(11.) paragraph a Instream Monitoring - remove one of the
downstream sampling points. Data does not support the need for two sampling
locations. Change the reference of outfall 002 to outfall 007.