NC0004774_Fact Sheet_20191217

DEQ/DWR
FACT SHEET FOR NPDES PERMIT DEVELOPMENT (Major Mod)
NPDES No. NC0004774
FACILITY INFORMATION
Permittee:
Duke Energy Carolinas, LLC
Permittee Address:
526 S. Church Street, Mail Code EC3XP, Charlotte, NC 28202
Facility Name:
Buck Combined Cycle Station (formerly Buck Steam Station)
Facility Address:
1385 Dukeville Road, Salisbury, NC 28146
Facility County:
Rowan
Facility Type:
Industrial — Steam Electric Power Generation
SIC Code(s):
4911
Permitted Flow:
Not Limited
Facility Status:
Existing
Waste Type:
Industrial
WWTP Grade:
PC-1
WATERBODY INFORMATION
ADDITIONAL INFORMATION
Waterbody Name:
Yadkin River
Regional Office:
Mooresville
Classification:
WS-V
USGS Topo Quad:
E17NW
Subbasin:
03-07-06
Permit Action:
Major Modification
HUC8:
03040102
Permit Writer:
Sergei Chernikov, Ph.D.
Drainage Area (miz):
3,452
Date:
October 28, 2019
Summer 7Q10 (cfs):
1,030
ij
Winter 7Q10 (cfs):
1,480
Average Flow (cfs):
4,960
Listed:
Not for POCs
IWC (%):
0.1%, 0.3%, 0.7%, & 100%
I. PROPOSED PERMIT ACTION
Duke Energy Carolina, LLC, has applied for a Major Modification to permit NC0004774 for its Buck
Combined Cycle Station (formerly, the Buck Steam Station). The Division of Water Resources has
reviewed the application and additional information submitted by Duke Energy and has made a tentative
determination to grant this request for a Major Modification.
Duke Energy requests to remove the following condition from Outfall 001A and Outfall 006: "The daily
average temperature of the effluent shall be such as not to exceed 10°C (50°F) if the daily average intake
temperature is below 2.5°C (36.5°17), and shall not exceed two times the intake temperature (°F) minus 23
if the daily average intake temperature ranges from 2.5°C (36.5°F) to 12.8°C (557) when only units with
the same control system are operating."
This requirements originates from an EPA nomograph from 1976 as the basis for the restrictions to
protect aquatic life from cold shock due to the thermal load from the retired Buck Fossil Steam Station.
This was first approved by North Carolina DENR in 1993. Additional delta T thermal limits intended to
protect warm water fish from cold shock in the event of a winter season plant shut -down event.
Historically, fossil steam stations could operate units separately, thus varying discharge flow and heat
load to the receiving stream. If all units functioned either on one control unit or as autonomous units, this
configuration could have impacts on the receiving stream if all units were shutdown at once versus
scaled over time. If all steam units were online, withdrawing water, heating it, and then discharging the
heated effluent, losing all units at once would cause a shock to the receiving stream and the aquatic life
surrounding the discharge point. The thermal rise calculation paired with the control unit designation
seeks to regulate the potential thermal shock of losing one or multiple operating units. Combined cycle
plants discharge significantly less heated effluent, i.e. approximately 0.6 MGD compared to 170 MGD,
than the demolished steam station, and have cooling towers that help regulate the effluent discharge
temperature.
Therefore, this condition is no longer applicable. The Water Sciences Section reviewed this request and
did not have any objections against eliminating it.
Fact Sheet—NPDES Permit Renewal
Duke Energy — Buck Combined Cycle Station — NC0004774
Page 1